
==== Front
Pain Ther
Pain Ther
Pain and Therapy
2193-8237
2193-651X
Springer Healthcare Cheshire

38980601
630
10.1007/s40122-024-00630-5
Original Research
Potential Cost Savings with 60-day Peripheral Nerve Stimulation Treatment in Chronic Axial Low Back Pain
Sheth Samir J. 1
Mauck William D. 2
Russo David P. 3
http://orcid.org/0000-0001-5350-2272
Keuffel Eric L. ekeuffel@hfaai.net

4
Gunnarsson Candace L. 5
Stultz Mark 6
McGee Meredith J. 6
Huntoon Marc A. 6
1 https://ror.org/0060avh92 grid.416759.8 0000 0004 0460 3124 Sutter Health, Roseville, CA USA
2 https://ror.org/02qp3tb03 grid.66875.3a 0000 0004 0459 167X The Mayo Clinic, Rochester, MN USA
3 Columbia Pain Management, Hood River, OR USA
4 Health Finance and Access Initiative, Ardmore, PA USA
5 Gunnarsson Consulting, Jupiter, FL USA
6 https://ror.org/020bbbm37 grid.505283.9 SPR Therapeutics, Cleveland, OH USA
9 7 2024
9 7 2024
10 2024
13 5 11871202
6 5 2024
14 6 2024
© The Author(s) 2024
2024
https://creativecommons.org/licenses/by-nc/4.0/ Open Access This article is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License, which permits any non-commercial use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by-nc/4.0/.
Introduction

Chronic axial low back pain (CLBP) that is not responsive to medication management or physical therapy often requires significant clinical intervention. Several interventional pain management options exist, including a 60-day peripheral nerve stimulation (PNS) treatment. This economic evaluation investigated the potential for projected cost savings associated with prioritizing 60-day PNS treatment relative to a ‘standard of care’ (SOC) approach (where patients do not have access to 60-day PNS).

Methods

A decision tree (supervised machine learning) model tracked treatment progression across two hypothetical cohorts of US patients with CLBP in whom non-interventional options were ineffective (Cohort A: treatment starting with 60-day PNS followed by any additional interventional and surgical treatments versus Cohort B: standard of care interventional and surgical treatments without access to 60-day PNS). Treatment efficacy estimates were based on published success rates. Conditional on treatment failure, up to two additional interventions were considered within the 12-month time frame in both cohorts. SOC treatment options included epidural injection, radiofrequency ablation (RFA), basivertebral nerve ablation (BVNA), PNS permanent implant (PNS-PI), spinal cord stimulator (SCS) trial/implant, and spinal fusion surgery. Treatment choice probabilities in both cohort algorithms were based on clinician interviews. Costs were based on national Medicare reimbursement levels in the ambulatory surgery center (ASC) setting. Savings reflected the difference in projected costs between cohorts. A Monte Carlo simulation and sensitivity analyses were conducted to generate confidence intervals and identify important inputs.

Results

The treatment algorithm which prioritized initial 60-day PNS treatment was projected to save $8056 (95% CI $6112–$9981) per patient during the first year of interventional treatment relative to the SOC approach.

Conclusions

Use of the 60-day PNS treatment as an initial interventional treatment in patients with CLBP may result in significant savings for Medicare. Projected savings may be even larger for commercial payers covering non-Medicare patients.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40122-024-00630-5.

Keywords

Back pain
Cost savings
Interventional pain management
Health economics
http://dx.doi.org/10.13039/100019735 SPR Therapeutics issue-copyright-statement© Springer Healthcare Ltd., part of Springer Nature 2024
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pmcKey Summary Points

Chronic low back pain affects millions of adults (more than 10% of the US adult population) and is a leading cause of disability worldwide.	
For some, the pain does not respond to conservative treatment like medication and physical therapy and patients seek additional treatment options, which can be more invasive and expensive.	
If initial treatments fail to provide relief of back pain, pain physicians may recommend interventions such as anesthetic injections, nerve ablation procedures, neurostimulation implants, or surgery. Percutaneous peripheral nerve stimulation (60-day peripheral nerve stimulation, PNS) is a recently introduced neurostimulation technology that is implanted in the back for 60 days and has been shown to provide durable back pain relief.	
The goal of this work was to compare the healthcare costs associated with the treatment of low back pain for two different treatment strategies: Cohort A (treatment starting with 60-day PNS followed by standard of care interventional treatments) vs. Cohort B (standard of care interventional treatments for back pain).	
A mathematical decision tree model was programmed using validated methods to calculate the total costs for 12 months of back pain treatment for hypothetical patients in each treatment group (cohort).	
The model found that treatment starting with 60-day PNS may be approximately $8000 less expensive than treatment starting with other standard treatments for low back pain.	
Additional sensitivity analyses were completed and confirmed that the cost savings associated with 60-day PNS are preserved even if there are changes in the model (e.g., changes in the treatment costs, likelihood of use of each treatment, and efficacy of treatments).	

Introduction

With a prevalence of over 10% in the US adult population, chronic low back pain (CLBP), which is defined as low back pain with a duration of at least 12 weeks, contributes significantly to the burden associated with spine pain and is a leading cause of health care cost and disability in the US and globally [1–3]. A 2016 analysis of US health expenditures across 154 disease conditions ‘low back and neck pain’, which includes CLBP patients, was identified as the highest-cost condition with spending of $134.5 billion [1]. On a per-patient basis, a matched (age, gender, region) cost analysis in 2008 found that CLBP patients had significantly larger annual health care claims expenditures relative to patients without CLBP ($8386 vs. $3607) [4]. While conservative treatment, such as physical therapy and medication management, can effectively address symptoms and functional impairment in some patients, these conservative treatments fail to produce a substantial improvement in many patients and these patients may require interventional pain management, which is typically more expensive [5]. The patient population of interest for this study includes CLBP patients with moderate-to-severe axial back pain in whom conservative treatments have failed to provide sufficient relief and who are seeking further intervention.

Interventional treatment options for patients with CLBP that are unresponsive to conservative treatment include epidural injections, radiofrequency ablation (RFA), basivertebral nerve ablation (BVNA), permanently implanted peripheral nerve stimulation (PNS-PI), spinal cord stimulator (SCS) implant, and lumbar spinal fusion surgery [6–14]. As there are a range of potential causes for CLBP, many patients seek to address their CLBP with non-surgical interventions before proceeding to surgery. Concerns related to appropriate utilization of existing treatments and cost-effectiveness have emerged with respect to pain and CLBP. Recent evidence also suggests that the high cost and high frequency of surgical treatment of CLBP may be both inefficient and lead to suboptimal clinical outcomes [7, 10, 15]. In the wake of opioid overuse in the US, limited insurance coverage for select non-pharmacological treatment and variations in payment and coverage for more intensive interventions may lead to more expensive yet clinically inferior outcomes [7, 16]. As such, part of the motivation for this analysis is to inform potential solutions and improvements in existing explicit or implicit ‘step therapy’ approaches currently in place among insurers.

Recently, 60-day percutaneous peripheral nerve stimulation (60-day PNS) has ADDIN EN.CITE emerged as a new treatment option for patients with CLBP. With 60-day PNS, temporary stimulating leads are implanted in a minimally invasive procedure and connected to body-worn stimulators programmed for each patient to deliver comfortable electrical stimulation to the lumbar medial branch nerves (which innervate the spine) for up to 60 days for the treatment of CLBP (for additional details on the 60-day PNS implant and treatment details, see [17, 18]). Recent prospective clinical trials have documented effectiveness beyond 1 year following the 60-day treatment for patients with CLBP, without requiring a follow-on permanent implant, as has been typical in the application of neurostimulation therapies [17, 18]. Conventional, permanently implanted peripheral nerve stimulation (PNS-PI) typically involves permanent implantation of an implantable pulse generator and stimulating leads that provide continuous stimulation to the targeted nerves. Due to the invasiveness and cost of the permanent PNS-PI device and implant procedure, insurers and physicians typically require success with a trial system, to ensure the patient will respond to the permanent implantation (further increasing cost and invasiveness associated with system implantation). Sixty-day PNS is a different type of peripheral nerve stimulation (PNS) that is minimally invasive, percutaneous (i.e., not permanently implanted), and designed to be used over a fixed (60-day) treatment duration (additional details on the procedural application of 60-day PNS are described in the literature) [18]. In the literature, despite this short-term treatment period, 60-day PNS has been shown to provide sustained, long-term pain relief for at least 1 year after the short-term stimulation phase [17, 18]. Therefore, 60-day PNS may enable patients to avoid the need to progress to more invasive and costly interventions. While some 60-day PNS patients may have short-term pain relief that wanes over time and may lead to progression to PNS-PI or other interventions, some 60-day PNS patients may see long-term benefits that reduce the need for additional interventions and reduces CLBP treatment costs overall.

While clinical effectiveness is the primary determinant in evaluating the benefit of new technologies such as a 60-day PNS treatment, payers also review economic evidence to understand the financial impact of treatment choice. To our knowledge, there have been no prior studies examining the economics of 60-day PNS treatment. This economic evaluation quantified the projected 1-year, per-patient savings of a treatment algorithm which incorporated the use of a 60-day PNS treatment relative to a ‘standard of care’ (SOC) approach that did not. This analysis aims to clarify how treatment patterns for select CLBP patients impact cost.

Methods

Given the subjective nature of patient response in pain management and the uncertainty associated with whether a particular treatment will work effectively in any particular patient, this model measured the projected 1-year costs of up to three treatments across two separate patient cohorts. In the first hypothetical cohort (Cohort A), patients received the 60-day PNS as the initial treatment and adopted up to two additional treatments (conditional on failure) during the one-year duration of the model. The second hypothetical ‘standard of care’ cohort (Cohort B) excluded 60-day PNS as a treatment option and patients adopted up to three SOC interventions (epidural injection, RFA, BVNA, PNS-PI, SCS, surgery) over the course of a year. This model aimed to quantify the projected costs associated with adopting 60-day PNS as an initial treatment relative to a SOC approach.

Model Structure

A decision tree model (supervised machine learning algorithm) was applied and followed published guidance for economic evaluations in healthcare (Consolidated Health Economic Evaluation Reporting Standards or CHEERS methodology) [19–22]. See Fig. S1 for an example of decision tree model methodology used for this analysis, including a description of the types of input data, mathematical calculations, and outputs. Since health outcomes reported in the literature often were not reported beyond a 12-month window, the model focused on 1-year costs. For the proportion of patients known to be successful for a given treatment (based on 1-year data in published literature), no further treatments are sought. Additionally, to reflect real-world treatment utilization patterns, a small proportion of patients are assumed to opt out of future procedural interventions at various timepoints in the model for both cohorts, despite the lack of success up to that point (Figs. S.2 and S.3).

Patient Population of Interest

The patient population for this analysis was intended to represent a realistic cohort of patients with chronic axial low back pain seeking additional intervention after failure of conservative treatments. This model considered patients with moderate to severe chronic axial low back pain after failure of physical therapy and/or management via oral medications, while excluding those with prior surgery, radicular or radiating leg pain, stenosis, or sacroiliac joint involvement. Given that back pain is often a multifactorial condition with multiple etiologies [23] and the intervention of interest (60-day PNS) has been successfully used to treat this patient population [17, 18], this analysis explored outcomes among a hypothetical pool of patients who could go on to receive a variety of treatments with standard of care without access to 60-day PNS, although not all patients are assumed to be candidates for all treatments. As described in more detail below, a panel of highly specialized interventional pain management physicians used their expertise to predict the likelihood that patients qualify for certain interventions when determining the treatment choice probabilities for the model. Treatment probabilities in the model therefore account for a combination of patient factors in determining eligibility for a specific intervention and patient preference, and as such, some treatments are more or less likely to be received by a hypothetical patient than others (see Model Inputs – Treatment Probabilities). Further, given variation in how CLBP is treated, additional sub-analyses were used to explore different patient populations, such as a more restrictive set of treatment options, which may reflect value in a more refined subpopulation of patients who have exhausted the least invasive interventions. This article is based on previously conducted studies and does not contain any new studies with human participants or animals performed by any of the authors.

Model Types

The base case ‘deterministic’ model calculated the mean projected total 1-year savings associated with 60-day PNS treatment at the start of interventional care relative to SOC. In addition to the deterministic model, Monte Carlo simulations were conducted to account for variation across model inputs and to provide 95% confidence intervals for the cost of care. Each simulation ran 10,000 trials in which model inputs were randomly chosen from their specified distributions (Supplementary Material Tables S.13–S.15). The mean and median (5000th) outcome values as well as the 250th and 9750th largest estimates were determined to generate 95% confidence intervals (CIs). Sensitivity and scenario analyses highlight the key inputs that shift the projected difference in costs per patient between the 60-day PNS cohort relative to the SOC cohort. Models were programmed using TreeAge Pro v.2023 (Deterministic Model) and @Risk v8.5.0 within Microsoft Excel (Monte Carlo Simulation).

Model Inputs

Three types of inputs were used for the model: (1) Costs (per treatment), (2) Treatment efficacy, and (3) Treatment probabilities (treatment algorithm). The inputs are sourced from Medicare reimbursement CPT (Current Procedural Terminology 2023, American Medical Association) and DRG (Diagnosis Related Group) codes (cost/reimbursement measures), peer-reviewed literature (efficacy measures) and a panel of practicing physicians (treatment algorithm). Figure S.1 illustrates the model methodology with an example of a simplified decision tree model architecture, showing how the input data (i.e., treatment costs, treatment efficacy rates, and treatment probabilities) are used to calculate a mean cost of treatment for each treatment algorithm.

Cost Inputs (per Treatment)

Cost inputs reflected the 2023 Medicare (national US average) reimbursement payments both for Ambulatory Surgery Center (ASC) payment and physician reimbursement [24]. In the base-case model, two leads were required for PNS-PI and 60-day PNS treatments, as well as for SCS implants. Prior to initiating a sequence of treatments, a diagnostic “bundle” (i.e., costs associated with diagnostic testing and imaging required to inform selection of initial interventional treatment) a cost of $1500 was assumed to help assess the optimal treatment pathway (which should account for physician visit and diagnostic procedures such as MRI to establish the treatment approach). The diagnostic bundle excluded conventional trial lead placements for permanent PNS or SCS procedures, which are considered separately. In a small share of cases, patients forgo any interventional treatment and a maintenance cost of $500 was applied for the balance of the year.

As most of the procedures are minimally invasive (with the exception of lumbar fusion surgery) and are generally completed on an outpatient basis, the CPT codes for relevant treatments were used to estimate costs (Table 1, Supplementary Tables S.1–S.12). In the case of permanently implanted neurostimulation devices (PNS-PI, SCS), where there is a potential for a trial period, or explant after failure of the implanted neurostimulator, relevant costs for each of these separate CPT events were included.Table 1 Cost summary: base-case decision tree model inputs

Treatment	ASC projected costs	Inpatient cost	
Trial (if needed)	Primary procedure	Removal (if needed)	
Epidural1	–	$1665	–		
RFA2	–	$2360	–	–	
BVNA	–	$10,399	–	–	
60-day PNS3	–	$11,681	–	–	
PNS-PI (Permanent)4	$11,681	$31,176	$2468	–	
SCS5	$10,450	$36,787	$2196	–	
Surgery	–	–	–	$35,079	
RFA radiofrequency ablation,), BVNA basivertebral nerve ablation, 60-day PNS peripheral nerve stimulation, PNS-PI PNS-permanent implant, SCS spinal cord stimulator

1On average, there are 2.4 epidural rounds per year per treated patient. Each epidural is assumed to be bilateral and has two levels

2RF ablation costs per session ($2360) are multiplied by 1 + the probability of repeat RFA within 1 year (pr = 0.477) or 1.477. Each RF ablation is assumed to be bilateral with two levels

3Assumes two leads in ASC setting. No reimbursement associated with removal

4PNS-PI primary procedure cost includes the cost of two leads ($11,681) and the neurostimulator ($19,495). With respect to trial costs, the model assumes that trial leads are not required in the 60-day PNS cohort since 60-day PNS substitutes as a diagnostic. For those receiving PNS-PI in the SOC arm, 33% may occur without a trial

5SCS trial costs assume two leads. Primary SCS procedure includes the reimbursement for the neurostimulator and the reimbursement for two percutaneous leads or a paddle lead. In the model, 15% of SCS primary procedures use a paddle and the balance use two percutaneous leads

There are unique aspects related to costs for (A) treatments that may require more than one administration to maintain efficacy within a calendar year (RFA and epidurals), (B) permanently implanted PNS systems, and (C) surgery. In the case of RFA, model costs accounted for the probability of retreatment within the first year (on average 48% of patients receive a second RFA within a year) [25]. The model also assumed that 2.4 epidural injections are required based on previously published analysis [26]. In Cohort A, when 60-day PNS failed to provide sustained relief in the first year, 25% were assumed to proceed to permanent PNS (without trial costs), as short-term response to 60-day PNS was assumed to substitute as the diagnostic pre-requisite (Fig. S.2) and 75% proceeded to other diagnostics and SOC interventions. For patients in the Cohort B (SOC) who received initial treatment with PNS-PI, the probability of treatment success following a PNS system trial is explicitly included separately from the probability of success with the permanent device, so costs are realized separately in the first (trial) and second (permanent implant) stage in the case of PNS-PI. Use of trial leads were assumed to be required in 67% of PNS-PI implants (as a recent PNS system has been approved that may not require a trial and this study assumes that one-third of PNS-PI patients use this approach) [27]. As such, the attendant costs of the permanent device are only accrued after the initial trial phase. Aside from these two cases, the costs and probabilities of PNS-PI system are jointly bundled in the rest of the model. In the case of the institutional payment for inpatient surgery, the model relied on the weighted mean of DRG payments in lumbar fusion cases with/without major complications ($31,840; See Supplementary Material Table S.12) for lumbar fusion from 2020 (the most recent year available from Medicare data) for cases with and without complications and were updated for medical inflation on the basis of the US Medical CPI (Consumer Price Index) (an increase of 5.3% to $33,528). The 2023 CPT cost of physician services ($1551) was also included in the overall surgical costs. In some cases, providers may use slightly different CPT codes for provision of services, but costs of alternate approaches fall within the 10% range used for sensitivity analyses. Cost estimates in the current study also focus just on the cost of major interventions. Medication costs, outpatient follow-up, and other minor costs are not modeled.

Treatment Efficacy

For each of the seven treatments considered in the model, 1-year efficacy probabilities aimed to reflect the likelihood that the treatment sufficiently addresses pain and functional status of the patient (so as to preclude utilization of alternative treatments for the remainder of the year), as found in peer-reviewed published literature. Table 2 summarizes the anticipated efficacy for each treatment based on published estimates [6, 17, 27–42]. Two important concepts with respect to efficacy are (A) the target patient profile and (B) the variety of efficacy measures used across different studies. When selecting published studies for efficacy estimates, this model focused on studies with similar target patient profiles, where possible. While efficacy studies do not necessarily match all these criteria, the literature estimates were evaluated in light of this optimal patient profile. For example, in the case of epidural efficacy, studies and reviews suggest that efficacy is limited in non-radicular back pain (especially over the course of a year) and a durability of effect occurs over short durations (< 2 months) so a lower bound estimate (0.22) was used as a base case (a more aggressive efficacy estimate would be closer to 0).Table 2 Efficacy summary: Base-case decision tree model inputs (deterministic model)

Treatment	Efficacy probability estimate (1 year)	Low back pain efficacy measure(s)1	Source(s)	
Epidural2	0.22	NRS	Chou (AHRQ, 2015), Murthy (Pain Medicine, 2014)	
RFA	0.46	NPRS, NRS, or VAS	Van Kleef 1999; Pevsner 2003; Juch 2017; Schneider 2020; McCormick 2023	
BVNA	0.64	NRS or VAS	Conger (Pain Medicine, 2022)	
60-day PNS3	0.58	BPI-5	Gilmore (2021, 2023)	
PNS-PI (Permanent)4*	0.67	VAS	Gilligan 2023	
SCS*	0.78	NRS or VAS	Kapural 2015; Al Kaisy 2017; Veizi 2017; Al Kaisy 2020; Fishman 2021; Kapural 2022	
Surgery	0.59	MCID	Snoddy 2016; Chotai 2015	
RFA radiofrequency ablation,), BVNA basivertebral nerve ablation, 60-day PNS peripheral nerve stimulation, PNS-PI PNS-permanent implant, SCS spinal cord stimulator

1BPI-5 = Brief Pain Inventory (Question 5, average pain score), VAS = Visual Analog Scale, NRS = Numerical Rating Scale, MCID = Minimum Clinically Important Difference. Generally, a clinically significant (≥ 30%) or substantial reduction (≥ 50%) in pain scores were used, however the MCIDs varied by intervention and prospective clinical trial methodology

2While Chou’s broad review of papers found that there was “no difference in pain, function or surgery likelihood” in patients treated with epidurals relative to placebo. As such, the paper uses a lower bound reported in the Murthy (2014) paper (0.22) as a reasonable base case estimate

30.58 is the share of patients with clinically significant reduction in pain intensity at 14 months

40.67 is the share of participants with clinically significant reduction in back pain intensity at 12 months

*The probability of PNS or SCS system explant was equal to 1-the success rate for the treatment (SCS:1–.78 = .22; PNS:1–.67 = .33)

Current research comparing various approaches to CLBP evaluation indicate that no one approach is currently favored as the dominant paradigm [43]. Further, there are multiple measurement approaches to assess efficacy of pain interventions [43]. In this analysis, tools include generalized and pain-specific measurement tools such as the Brief Pain Inventory (BPI, Question 5, Average Pain), Visual Analog Scale (VAS), and Pain Relief Numeric Rating Scale/Numeric Rating Scale (PRNRS/NRS), depending on the methods used in the peer-reviewed, published literature for each intervention. Table 2 summarizes the efficacy values applied in the base-case model. In the case of 60-day PNS, the primary endpoint was prospectively defined as the share of participants experiencing “clinically significant reductions” (< 30% reduction in intensity as measured by BPI-5) in chronic LBP relative to initial pain intensity reported for each patient [17, 18]. The RFA, SCS, and surgery efficacy measures also reflect the mean estimate from recent peer-review publications focused on CLBP populations. The model assumes that efficacy estimates from the literature are appropriate proxies for the patient type presented to an expert panel of interventional pain management physicians to determine treatment probabilities. Sensitivity analyses help elucidate the degree to which each of the efficacy estimates influences cost savings. The sensitivity analyses also show how results would change if the modeled efficacy figures for the subgroup of interest differs significantly from those reported in the literature.

Treatment Probabilities (Treatment Algorithms)

The treatment progression or treatment algorithms in the model were based on pain management physician expert opinion, collected prior to generating model output. There were three phases of development for the treatment algorithms for each cohort of patients. First, a team with expertise of the research and development and commercial market for pain treatments developed an initial patient type (exclusion and inclusion criteria) and treatment algorithm guide (e.g. share of patients receiving first, second and third line treatments). Second, an online survey of pain management physicians (n = 22, survey available upon request) and an in-depth-interview with a key physician advisor (n = 1) updated the patient description (inclusion/exclusion criteria to define the optimal patient characterization for this study), treatment options (added BVNA) and updated probabilities for first line and subsequent treatments (by cohort). The discussion also confirmed that no more than three treatments was an appropriate cap for a 1-year duration. At this juncture, it was clear that longer in-depth-interviews with physicians with experience using each of the treatments was more conducive and a less confusing format for the nuance of understanding relevant treatment sequences in this specific patient population. As such the final phase of development for the treatment probabilities were updated through a series of phone interviews with an expert panel of practicing interventional pain management physicians (n = 6 physicians) to outline typical treatment patterns for patients with axial low back pain. As there is variation in adoption by insurers across treatment modalities (a factor that can limit treatment recommendation and use by physicians), the expert panel (which included two of the authors) was comprised of a convenience sample of interventional pain management specialists experienced with these CLBP treatments (i.e., familiar with the clinical tradeoffs and appropriate use of the relevant technologies, some of which are recent innovations). The panel also reviewed the 2nd round and 3rd round treatment probabilities as well as the opt-out (i.e., where patients choose no further treatment) estimates.

In the case of the 60-day PNS cohort (Cohort A) there are 26 potential treatment pathways patients follow (Supplementary Material Fig. S.2). The three main ‘branches’ of this group are (A) individuals whose CLBP is successfully addressed with the 60-day PNS treatment (58% of all patients in the hypothetical cohort), (B) those who use the initial 60-day PNS treatment before advancing to a permanently implanted PNS system (the 60-day PNS system effectively validating the use of permanent PNS system), and (C) a sub-group that proceeds on to other treatment options after diagnostic assessment. In the second group (25% of the 60-day PNS treatment patients with pain relief that is not sustained), PNS-PI is attempted. If PNS-PI is ineffective, half of the remaining patients attempt SCS and the balance have no additional procedural intervention. In the remainder of the 60-day PNS treatment patients who do not sustain pain relief with 60-day PNS, additional diagnostic testing is conducted for 90% of the group and 10% opt out of future treatment. Among those that receive the diagnostic bundle, subsequent treatment probabilities for the second treatment are 60% RF ablation, 15% epidural, 12.5% BVN ablation, 7.5% SCS and 5% surgery. Conditional on failure of the second treatment, the third treatment is SCS with two exceptions: (1) there is no treatment within the remainder of the 12-month window following surgery and (2) the final treatment after failed SCS is RF ablation.

In the case of the SOC cohort (Cohort B), there are 38 potential clinical pathways in the model (Supplementary Material Fig. S.3) after patients receive the initial diagnostic bundle. The model assumes 2% of patients opt out of treatment after diagnostic testing and the balance proceed to an initial interventional treatment in the following proportions (based on recommendations from the physician expert panel): 50% RF ablation, 15% epidural, 12.5% BVNA, 10% permanent PNS, 7.5% SCS, and 5% surgery. Conditional on failure, some patients will opt to stop treatment (the share depends on the initial treatment) and the balance move on to SCS as a second treatment with two exceptions: (1) after epidural failure, 25% will opt for SCS and 75% will select surgery, and (2) after SCS, patients proceed to RF ablation. If the second procedure fails, the model generally assumes that half of the remaining patients will forego treatment and the balance will proceed to surgery with two exceptions: (1) after the surgery/SCS treatment combination, no third treatment is attempted (the remaining options are all less intensive interventions than surgery and SCS) and (2) after the epidural/surgery treatment combination, 75% of patients attempt SCS and 25% seek no further treatment. The model assumes that efficacy of treatment stays constant independent of when the intervention occurs and both cohorts have a maximum of three clinical interventions.

Sensitivity analyses were conducted to detect which inputs impact the magnitude of key outcome variables—in this case the savings associated with the algorithm which prioritized 60-day PNS treatment. In the sensitivity analyses, all inputs were varied univariately ± 10%, or ± 20% in an additional sensitivity analysis scenario) and those which shift output to the greatest degree were ranked. For select inputs, there is a natural ceiling or floor (0% or 100%), which constrains the ± 10% value. Scenario analyses which involve shifting multiple inputs jointly were also conducted to add further robustness to the findings.

Results

Sixty-day PNS vs. SOC: Base-Case Results

Projected costs for major procedures related to treatment of CLBP were lower in the cohort of patients who initially receive 60-day PNS treatment relative to the Standard of Care patient cohort (Table 3, Figs. 1 and 2). In the ASC setting, projected costs were $22,687 (95% CI $21,069–$24,341) for Cohort A (the group that initially receives 60-day PNS treatment) and $30,743 (95% CI $29,486–$32,063) in Cohort B (the SOC group), a savings of $8056 (95% CI $6112–$9981) per patient.Table 3 Projected 1-year cost and savings of chronic low back pain treatments (by treatment approach)

Treatment approach	Savings (SOC – 60-day PNS)	
Initial 60-day PNS cohort	SOC cohort	
$22,687 ($21,069-$24,341)	$30,743 ($29,486-$32,063)	$8056 ($6112-$9981)	
95% confidence intervals in parentheses (based on Monte Carlo simulation 2.5 percentile and 97.5 percentile estimates)

Fig. 1 Expected 1-year expenditures, by treatment regimen (histogram, n = 10,000 draws)

Fig. 2 Expected 1-year savings (histogram, n = 10,000 draws)

Sensitivity Analyses

Sensitivity analyses detect which inputs impact the magnitude of key outcome variables and are shown in the Supplementary Material (Table S.16). The most important inputs were the probability of intervention for SOC patients, and the cost and efficacy of 60-day PNS. These ‘Top 3’ inputs impact the early stages of the decision process, which have a relatively large influence over the savings result. As the probability of intervention increases in the SOC arm, projected savings associated with initiating treatment with the 60-day PNS also increase since projected costs in the SOC arm rise.

Scenario Analyses

In addition to sensitivity analyses, when one variable is shifted while all others remain at ‘base-case’ values, scenario analyses, which incorporate joint changes across multiple inputs at the same time, were also conducted to examine the robustness of the savings result under different scenarios. For example, when the model assumed an even wider distribution range of 20% for model inputs (base-case range 10%), the width of the confidence intervals for both the 60-day PNS cohort and the SOC cohort expanded, but the savings result remained significant (Table S.17 and Fig. S.4).

A second set of scenario analyses evaluated the level of savings when efficacy levels were increased by 20% and costs were decreased by 20% for each of the treatments aside from 60-day PNS. As reported in Table S.18, the savings associated with the 60-day PNS remain positive in all scenarios but are smaller relative to the level in the ‘base-case’ scenario ($8056). In the six cases where one treatment is adjusted, savings levels were between $5025 (SCS efficacy increased 20%, SCS costs decreased by 20%) and $7715 (epidural) but savings remained positive (> $0) for each scenario. Scenarios 7–9 of Table S.18 show how savings range if multiple treatments are adjusted jointly. One may consider these “worst-case” scenarios from the standpoint of finding savings in the 60-day PNS arm. When the three less expensive treatments (epidurals, RFA, BVNA) are assumed to have more efficacy and even lower cost, savings remain positive ($5836; Scenario 7). In the scenario when each of the more intensive treatments (PNS-60, SCS, surgery) are assumed to be lower cost and higher efficacy; savings remain robust but decline to $3489 (Scenario 8). If all six of the “competing” treatments are assumed to have lower price and higher efficacy, savings fall to $1740, but remain positive. Even in a “worst-case” scenario the outcome is robust and the savings remain above $0. Findings from scenario analyses are contingent on the validity of the base case model.

A final set of scenario analyses estimated the savings under conditions in which a more limited set of treatment options are assumed for patient populations that are more likely to require more intensive (i.e., more invasive and costly) options than in the base-case analysis (Table A.19). These analyses may be more reflective of treatment choice in situations where physicians are not as familiar with emerging treatment options such as BVNA or for patient subgroups that have exhausted less invasive interventions. For example, if epidurals and BVNA are excluded as potential treatment options (probabilities are set to 0), then savings increase to $10,326 (vs. $8056 in the base-case). In a more restrictive subgroup of patients (where epidurals, BVNA and RFA are all excluded) savings increase to $21,571. Essentially as the lower-cost SOC treatment options such as epidurals, RFA, or BVNA are excluded (either based on patient type or physician application of technologies within the relevant patient pool), the savings associated with 60-day PNS increase substantially. Due to variations in epidural approaches, an additional sensitivity analysis in which one, instead of two, epidural injections are administered (i.e., reimbursement per epidural treatment were reduced by half) indicated that savings would fall only slightly from $8056 (base-case) to $7847.

Discussion

This economic evaluation quantified the projected savings of a 1-year treatment algorithm that incorporated a 60-day PNS treatment relative to a ‘standard of care’ (SOC) approach that did not. The treatment algorithm, which prioritized initial use of a 60-day PNS treatment, is projected to save $8056 (95% CI $6112–$9981) per patient during the first year of interventional treatment relative to the SOC approach. Further, both univariate sensitivity analyses and multiple scenario analyses support the findings that initiating treatment with 60-day PNS lowers 1-year costs relative to a SOC approach under a variety of circumstances.

Annual cost associated with up to three intensive treatments are naturally larger than the cost of an ‘average’ year for CLBP patients. The 1-year costs in both the 60-day PNS and SOC cohorts are substantially larger than the annual cost per CLBP patient year as estimated in a prior data analysis ($12,625 in 2023 $US after increasing the previously discussed $8,386 by the CPI Medical Care cost growth in the 50.6% between 2008 and 2023) [4]. This difference reflects the fact that, by construction, the 60-day PNS simulation model focused on the year when major interventions are implemented whereas other research may cover time periods both prior to and after the implementation of high-cost interventions. Costs are also highly variable in cross-sectional analyses of the CLBP population and in part such variability may reflect these “high-cost” episodes associated with intensive interventions such as surgery or SCS. Payers of CLBP costs may help reduce both the magnitude and variability of costs during these “high-intensity” episodes of care by opting for treatment algorithms such as 60-day PNS that has the potential to more efficiently address morbidity relative to current treatment patterns. Future research may help refine the optimal population sub-groups and alternative treatment algorithms to address cost and cost-effectiveness as additional technologies emerge. Nevertheless, our results suggest that 60-day PNS is a cost-effective treatment for select CLBP patients and merits coverage and consideration as part of an early intervention in a ‘step therapy’ care pathway for US healthcare payers.

The savings estimate is specific to the homogeneous sub-group—a group of patients that could potentially be relevant candidates for each of the seven treatments offered in the two care pathways. Cost estimates also are focused on major interventions (and explants) rather than ongoing cost such as follow-up outpatient visits or medications. Once adoption of all the treatments is more widely available, more heterogeneous patients may ‘sort’ into different treatment regimens based on further refinement of patient variables.

Limitations

There are some important caveats to consider when interpreting the direction and magnitude of the findings. First, given the limited claims and comparative data available, this model relies on treatment protocols based on the expert opinion of interventional pain management physicians that regularly treat CLBP and are familiar with each of the technologies assessed in the study. Expert opinion, especially within the field of pain medicine, can vary substantially based on physician preferences, patient population, and perceived treatment effectiveness, therefore a limited physician sample was used. Since cost savings with 60-day PNS is robust given all sensitivity and scenario analyses, it is believed that the differences in treatment utilization not studied here (e.g., use of other types of surgery, increases in the proportion of patients receiving certain treatments first, etc.) are unlikely to overturn the model outcome. Future analyses using healthcare claims data may offer an alternative and more generalizable means to track patient costs and outcomes across treatments, if the analyses can avoid misclassification, identify relevant CLBP patient types and accurately assess the patient experience over time.

Second, this study relies on Medicare reimbursement to measure the payer costs linked to various treatments. Generally, commercial insurers pay substantially more for the same service relative to Medicare payments. As such, the savings calculated in our Medicare-based payment model may underestimate the savings that commercial payers would realize for the same type of patients. Additionally, Medicare payments for outpatient services in hospital outpatient (HO) settings typically are larger than ASC settings. To the degree this is the case in CLBP, the savings accruing to Medicare in the HO setting may exceed the findings found with this model. In order to focus on pure financial impacts from the health payer perspective, impacts on productivity or absenteeism, quality of life, and broader social costs were not considered within this model. Productivity or absenteeism impacts may include sick days, changes in productivity at work, and potential reductions in individual or family income. Such costs can be significant, even within the 1-year time frame, as prior estimates of CLBP costs suggest the indirect and social costs can exceed direct medical costs [44]. Future studies should further examine if treatments can reduce the societal burdens associated with CLBP, including impacts on patients’ QoL (quality of life) and impact on indirect costs borne by employers, families, and other stakeholders.

Physicians in the expert opinion panel may differ from the general population of pain management physicians due to A) the small sample size and B) the more regular use of recent innovations (60-day PNS and BVNA) which may differentiate them from the broader pain management provider population. While this preference for innovation helps map out the potential value within their practices, until others adopt innovation (and in a similar manner) – the treatment patterns (first-, second-, and third-line therapies; opt out probabilities) and economic outcomes found in the model may differ from the general pain management community. There may also be patient- or physician-level differences in how each intervention is applied (lead placement, etc.) that may influence the expected efficacies used in the model for each intervention (Table 2). This study also did not include engagement with CLBP patients, although the physician-guided treatment progression sought to represent typical patient use patterns demonstrated by patients in their respective practices. Future studies could benefit by incorporating perspectives of both physicians and patients and considering how specific patient symptomatology further impacts treatment utilization and costs.

The model is truncated at 1 year to keep the model tractable, transparent, and relevant to payers with a shorter-term focus on costs. The model includes treatments that often lose efficacy or require multiple repeat treatments over longer periods, so longer-term costs over multiple years may differ. Given the recency of innovation in the space, longer-term efficacy, and demonstration of extended durability are still unknown and will certainly impact patient costs. Efficacy levels are based on published literature and assume that the published figures are reasonable proxies for the efficacy that would occur in the more refined patient characterization applied in the model.

Lastly, savings are likely a function of patient selection. In the model, a large share of patients received either RFA or epidural treatment. Both are substantially less costly than the five other interventions in the model but have effects that diminish over time and are perhaps less appropriate for a sub-group of patients with more severe clinical presentation and/or long-standing disease. In these more severely affected patients, the cost savings are larger than in the base-case model (as demonstrated in the final scenario analyses), which suggests that the base-case is a relatively conservative model given the significant proportion of patients who receive lower cost treatment options. Future models could also compare initial treatment using other alternatives as an initial intervention, and these approaches may also wish to expand the time horizon to address waning efficacy and durability over time (esp. of some of the lower cost options). However, some treatments such as BVNA have stricter eligibility criteria (i.e., requires specific documented findings on MRI), so this same analysis would not be possible for BVNA (i.e., 60-day PNS lends itself well to the analysis depicted here because of the broad variety of interventions that patients might be able to avoid by using 60-day PNS). While the preferred approach to treatment may eventually differ depending on the patient’s characteristics, this analysis suggests that 60-day PNS can be a valuable solution for insurers covering patients with axial CLBP that is unresponsive to prior conservative treatment.

Conclusions

Early utilization of 60-day PNS treatment for CLBP may prevent the use of more expensive interventions or more invasive approaches in select patient populations. This economic evaluation found significant cost savings in the ASC setting when 60-day PNS treatment was used as a first-line interventional treatment after more conservative therapy options failed to address pain sufficiently.

The model findings suggest that using 60-day PNS as an initial treatment approach for patients with moderate to severe CLBP may substantially offset future potential utilization and costs of other options that are frequently used as ‘standard of care’ treatments in similar patients.

Supplementary Information

Below is the link to the electronic supplementary material.Supplementary file1 (PDF 835 KB)

Acknowledgements

We thank the participants of the study.

Author Contributions

Concept and design: Keuffel, Gunnarsson, Sheth, Huntoon, Stultz, McGee. Acquisition of data: Keuffel, McGee. Analysis and interpretation of data: Keuffel, Gunnarsson, Sheth, Mauck, Russo, Huntoon, Stultz, McGee. Drafting of Manuscript: Keuffel. Critical revision of paper for important intellectual content: Keuffel, Gunnarsson, Sheth, Mauck, Russo, Huntoon, Stultz, McGee. Administrative, technical and logistical support: Keuffel, McGee. Statistical Analysis: Keuffel, Gunnarsson, McGee. Supervision: Keuffel, Gunnarsson, Sheth, Huntoon, Stultz, McGee.

Funding

This research was supported by SPR Therapeutics (This includes Rapid Service and Open Access fees). The funder reviewed the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript, and decision to submit the manuscript for publication.

Data Availability

Data sharing is not applicable to this article as no datasets were generated or analyzed during the current study.

Declarations

Conflict of Interest

Eric Keuffel, Candace Gunnarsson, and Samir Sheth receive consulting fees from SPR Therapeutics. Mark Stultz, Meredith McGee and Marc Huntoon are employees of SPR Therapeutics. William Mauck and David Russo have nothing to disclose. Dr. Sheth and Dr. Huntoon also served on the expert physician panel that determined treatment choice probability variables used in the model.

Ethical Approval

This article is based on previously conducted studies and does not contain any new studies with human participants or animals performed by any of the authors.
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