A single joint submission was received from Boston Scientific, Neuromodulation Systems, and Medtronic. This submission, which included an economic evaluation, was coordinated by the Association of British Healthcare Industries (ABHI). The Assessment Group also developed their own economic evaluation. Both the manufacturers' and Assessment Group's models used a similar structure.
The Manufacturers' Submission
The submission received from the manufacturers evaluated the cost effectiveness of spinal cord stimulation (SCS) for the treatment of neuropathic pain and modelled both failed back surgery syndrome (FBSS) (SCS with conventional medical management [CMM] compared with either CMM alone or repeat operation in combination CMM) and complex regional pain syndrome (CRPS) (SCS with CMM compared with CMM alone). Ischaemic pain conditions were not modelled. The model included two-stages: a decision tree for short-term treatment with SCS (first 6 months), followed by a Markov process for SCS treatment from 6 months to 15 years. Probabilities of events were based on data from the randomised controlled trials (RCTs) of FBSS and CRPS. The time frame in the second stage of the model was based on an observational study that investigated clinical predictors of outcomes for people using SCS systems over a 15-year period. Treatment success was defined as 50% or greater reduction in pain.
For FBSS, the model produced an incremental cost-effectiveness ratio (ICER) of 9,155 pounds sterling per quality-adjusted life year (QALY) gained when SCS in combination with CMM was compared with CMM alone. A comparison of SCS and CMM with repeat operation and CMM produced an ICER of 7,954 pounds sterling per QALY gained. For CRPS, the model produced an ICER of 18,881 pounds sterling per QALY gained for SCS and CMM compared with CMM. Sensitivity analyses demonstrated that the model was sensitive to assumptions about device longevity and device cost.
Assessment Group's Economic Evaluation of Neuropathic Pain
The Assessment Group developed a two-stage model, comprising a decision tree to 6 months with a Markov process extending to 15 years. Both FBSS and CRPS conditions were modelled using data from the two trials of FBSS and the trial of CRPS. For FBSS, SCS in combination with CMM was compared in the model with CMM alone, and with repeat operation in combination with CMM (the latter is referred to in the remainder of the document as 'repeat operation'). For CRPS, SCS in combination with CMM was compared with CMM alone. Patients entered into the second stage of the model in the same health state that they were assigned to at the end of the first 6 months (in the first stage of the model). The time frame was based on an observational study that investigated clinical predictors of outcomes for people using SCS systems over a 15-year period.
For FBSS, the ICERs for SCS in combination with CMM, when assuming device longevity of 4 years and using a device price figure of 9,000 pounds sterling, were 10,480 pounds sterling per QALY gained compared with CMM alone and 9,219 pounds sterling per QALY gained compared with repeat operation.
For CRPS, SCS in combination with CMM compared with CMM alone, when assuming device longevity of 4 years and using a device price of 9000 pounds sterling, produced an ICER of 32,282 pounds sterling per QALY gained.
The Assessment Group model – using utilities from the CRPS trial, a device cost of 9,000 pounds sterling and device longevity of 4 years – produced an ICER of 16,596 pounds sterling per QALY gained for SCS compared with CMM.
Assessment Group's Economic Evaluation of Ischaemic Pain
The Assessment Group did not carry out an economic analysis of critical limb ischaemia (CLI), but explored the cost effectiveness of SCS for the treatment of refractory angina (RA) using an alternative modelling approach. A threshold analysis was presented based on a mathematical model that incorporated data from a prospective observational study.
Consideration of Evidence
The Committee examined the economic modelling that had been carried out for the appraisal. It noted that both the model by the Assessment Group and that submitted by the manufacturers had a similar structure.
The Committee noted that there were a range of SCS systems available at different prices. The Committee heard from clinical specialists that one of the factors affecting the choice of device was the complexity of pain pattern and the extent of pain. For example, a person with a single painful limb may be expected to derive greater longevity from the same device than someone with a more complex pain pattern or greater body area affected. Clinical specialists suggested that device longevity may regularly exceed 4 years, even with a non-rechargeable device. The Committee therefore recognised that price and longevity may be interdependent and that longevity varies depending on an individual's pain characteristics.
The Committee considered the estimates of cost effectiveness for SCS in the treatment of FBSS. The Committee noted that the manufacturers' and Assessment Group's models produced similar estimates of the ICERs for the use of SCS compared with alternative treatments, and that these were less than 11,000 pounds sterling per QALY gained for the base-case analyses. The Committee was persuaded that the use of SCS for the treatment of FBSS would be a cost-effective use of NHS resources.
The Committee examined the estimates of cost effectiveness for SCS in the treatment of CRPS. It noted that the Assessment Group's and the manufacturers' models had used different sources of utility data and that neither captured the utility of a person with CRPS accurately, as one source was a trial of FBSS and the other a wider survey of neuropathic pain conditions. The Committee noted the additional utility data that had been provided by the Association of British Healthcare Industries (ABHI) on behalf of the manufacturers from the CRPS clinical trial. The Committee agreed that these utility data appropriately reflected a group of people with CRPS who may be treated with SCS and that these data should be considered as part of the appraisal. The Committee therefore examined an analysis completed using the Assessment Group's model that included the utility data from the CRPS trial. It acknowledged that the results of analysis using these data produced an ICER of less than 17,000 pounds sterling per QALY gained when using a device price of 9,000 pounds sterling. The Committee was also mindful of consultee comments that device longevity may be greater than the 4-year period used in the economic modelling. The Committee recognised that increasing device longevity would further reduce the ICER. The Committee was therefore persuaded that the use of SCS for the treatment of CRPS would be a cost-effective use of NHS resources.
The Committee noted that the manufacturers had not provided an economic evaluation of the use of SCS for ischaemic pain, and that the Assessment Group had only been able to complete exploratory threshold analyses for RA because of limited availability of evidence. Examining the analyses for RA, the Committee considered that their relevance was limited as they were based on a population of people for whom treatment with coronary artery bypass graft (CABG) or percutaneous coronary intervention (PCI) was suitable. However, these revascularisation techniques are often unsuitable for people with RA. The Committee concluded that although the clinical evidence suggested that there may be groups of people with RA and CLI who could benefit from SCS, there was insufficient evidence on survival and benefits in health-related quality of life (HRQoL), as well as on cost effectiveness. It therefore concluded that the use of SCS for the treatment of chronic pain of ischaemic origin could currently not be recommended.
See Sections 4.2 and 4.3 in of the original guideline document for a detailed discussion of the cost-effectiveness analysis.