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PROCESS vs. WA State SCS Study

PROCESS vs. WA State SCS Study. A Comparison of Study Design, Patient Population, and Outcomes August 29,2007.

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PROCESS vs. WA State SCS Study

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  1. PROCESS vs. WA State SCS Study A Comparison of Study Design, Patient Population, and Outcomes August 29,2007

  2. A non-randomized, prospective cohort study to describe costs, complications and patient outcomes among WA state Workers’ Compensation CBLP claimants in three treatment groups (SCS group, Pain Clinic group, Usual Care group) Observational Followed up to 24 months A prospective, randomized (1:1), controlled, multi-center trial to test the efficacy and cost-effectiveness of spinal cord stimulation (SCS) plus conventional medical management (CMM) vs. CMM alone for patients with failed back surgery syndrome (FBSS). Crossovers permitted at 6 months. Followed up to 24 months Study Design WA State PROCESS

  3. 18-60 years of age* Current WA state WC fund claim for a back injury (any duration)* 1 to 3 previous open lumbar spine surgeries (during current claim)* Current receipt of time loss compensation Pain radiating into one or both legs for more than 6 months Radicular pain greater than axial pain Average leg pain in the last month rated as 6 or greater on a 0-10 scale 18+ years of age Neuropathic pain predominantly in legs (>50%) VAS Pain intensity > 50 mm Symptoms >6 months following At least one anatomically successful surgery for herniated disc Inclusion Criteria WA State PROCESS * Criteria revised due to slow enrollment. Original criteria included age 18-55, claim <3 years’ duration, and 1 or 2 previous surgeries

  4. Previous SCS surgery Diagnosis of diabetes or cancer Unable to speak English or Spanish Progressive motor deficit or bony deformity or any contraindication for surgery Other clinically significant or disabling chronic pain condition Expected inability to receive or operate the SCS system History of: Coagulation disorder Lupus Diabetic neuropathy Rheumatoid arthritis Ankylosing spondylitis Active psychiatric disorder Other condition known to affect perception of pain Inability to evaluate treatment outcome Life expectancy <1 year Existing or planned pregnancy Exclusion Criteria WA State PROCESS

  5. Injured workers who are authorized by DLI for a SCS procedure are compared to two comparison groups Injured workers in this group were told that SCS would be covered if they participated in the study (was not otherwise) Workers potentially eligible for SCS were initially identified at clinic visits by health care providers who performed the SCS procedure. They were screened and send to DLI for administrative review and then U of W research team contacted worker for remainder of screening/invite Injured workers who meet the same clinical criteria as used for the SCS group and who have not been referred for authorization for SCS, but who have been referred to a multi-disciplinary pain clinic Workers were identified from DLI administrative databases at the time they were approved for the pain clinic evaluation They were screened and send to DLI for administrative review and then U of W research team contacted worker for remainder of screening/invite WA State Cohorts: What We Know About Cohort Assignment SCS cohort Pain Clinic cohort Usual Care cohort • Injured workers who meet the same clinical criteria as used for the SCS group, but who have not been referred for DLI authorization for SCS (Usual Care group) • Individuals were randomly selected from DLI administrative files • U of W research team contacted worker for all screening/invite Note: Patients were already referred, which leaves the possibility of selection bias.

  6. Primary: Leg pain (NPRS), physical disability (RDQ), and use of opioid analgesics Secondary: Back pain intensity, assessment of leg pain vs. 1 year prior, current work status, types of therapy used, mental health (SF-36), complications, device use, cost (to be reported in future publications) Primary: Proportion of patients achieving at least 50% leg pain relief at 6 months (VAS) Secondary: Improvement in back and leg pain, HRQoL (EQ-5D, SF-36), functional capacity (ODI), change in use of pain medication and non-drug therapy, patient satisfaction with treatment, incidence of adverse events, cost (to be reported in future publications) Primary and Secondary Endpoints WA State PROCESS

  7. No power calculations due to descriptive nature of study (post hoc noted) Target of 50 patients per group because the authors thought this number of patients could be recruited in a 1-year period Used both intent-to-treat and as treated principles ANOVA, chi-square and Kruskal-Wallis used at baseline ANCOVA with adjustment for select covariates used at follow-up Power calculation performed to determine adequate sample size Used both ITT and as treated principles Chi-square and t-tests used at baseline Linear and logistic regression with select covariates used at follow-up Also used step-wise, LOCF method, interaction terms, and completed sensitivity analysis Statistical Analysis WA State PROCESS

  8. Patient Flow WA State PROCESS Ineligible • PROCESS enrollments occurred between April 2003 and June 2005 • WA state enrollments occurred between December 2004 and June 2006

  9. Demographics & Baseline Characteristics (1 of 3) *PROCESS defined as FT or PT status; WA State defined as working or other (student/retired)

  10. Demographics & Baseline Characteristics (2 of 3) ^ Leg and back pain measured at baseline visit for PROCESS and in past month for WA state. 0-100 scale for PROCESS and 0-10 scale for WA state.

  11. Demographics & Baseline Characteristics (3 of 3)

  12. Results: Primary Outcome at 6 Months * Indicates a statistically significant difference ^ Adjusted logistic regression model

  13. Results: Primary Outcome at 12 Months * Indicates a statistically significant difference ^ Adjusted logistic regression model

  14. 24/52 patients assigned to SCS received the therapy; 20 were trialed and not implanted due to failed trial; 8 had not been trialed 31/51 patients assigned to Pain Clinic group received the therapy several times per week; 20/51 patients received the therapy < several times per week 54/56 patients assigned to Usual Care group completed the follow-up; 2 received SCS; 2 unable to contact. Percentage of Patients Receiving Their Assigned Treatment: 6-months WA State PROCESS • 48/52 patients randomized to SCS received the therapy; 4 were not implanted due to a failed trial • 48/48 patients randomized to CMM received the therapy

  15. Results: Secondary Outcomes ^ Adjusted analysis * Versus 2%, 2% and 9% at baseline for 6%, 2% and 1% RTW

  16. Results: Secondary Outcomes ^ 12-month data not yet finalized, 6-month data for secondary outcomes will be reported in forthcoming manuscript * Achieved statistical significance

  17. Brief Critical Review (1 of 2)* * Based on Delfini checklist: http://www.delfini.org/Delfini_Tool_StudyValidity_Short.doc

  18. Brief Critical Review (2 of 2) * Based on Delfini checklist: http://www.delfini.org/Delfini_Tool_StudyValidity_Short.doc

  19. 2b (at best) defined as an individual cohort study. If the cohort study is considered to be of poor quality, the level would be 4. Poor quality is defined as a study that failed to clearly define comparison groups and/or failed to measure exposures and outcomes in the same (preferably blinded), objective way in both exposed and non-exposed individuals and/or failed to identify or appropriately control known confounders and/or failed to carry out a sufficiently long and complete follow-up of patients. 1b defined as an individual RCT with a narrow confidence interval A wide confidence interval example provided by CEBM is when an ARR in an RCT is not statistically significant but whose confidence intervals fail to exclude clinically important benefit or harm. This does not apply to PROCESS. If PROCESS had <80% follow-up, it would be considered low quality and have a grade of 2b. This does not apply. PROCESS had 93% of patients contributing data at the 6-month primary endpoint and 88% at 12 months. Level of Evidence: Based on Oxford CEBM Tool* WA State PROCESS * http://www.cebm.net/index.aspx?o=1025

  20. Conclusions (1 of 2) • PROCESS is a RCT generating level 1b evidence in support of SCS for CBLP (FBSS) over CMM alone. Statistically significant, clinically meaningful improvements demonstrated for pain, function and QOL. • The WA State SCS study is a prospective, comparative cohort study generating level 2b evidence (at best) and potentially level 4 evidence of no significant benefit of SCS for CBLP (FBSS) over Pain Clinic or Usual Care. • PROCESS has external validity for non-WC FBSS patients, while the WA State study has external validity for WC FBSS patients only.

  21. Conclusions (2 of 2) • In the WA State study, the absence of information about how patients qualified for referral to SCS or Pain Clinic in addition to the non-experimental design opens the door for bias. • In the WA State study, attempting to improve pain, function and return to work in a cohort of WC patients injured on average 4 years prior to study enrollment could be considered a near fatal flaw. • We know from the literature that WC patients have poor outcomes and are unlikely to RTW • WC patients have the ability to be closely tracked/managed in terms of health services utilization. They are, in many ways, a captive population that could have been studied in a far more effective (i.e. experimental) manner. • The observational/naturalistic approach to the WA State study leaves the reader unable to draw conclusions about the effectiveness of one therapy option over another.

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