4.1 The committee considered the clinical evidence and noted the inconsistent results from the 2 randomised controlled trials (Kapural et al. 2016 and De Andres et al. 2017). In particular, the committee noted that Kapural et al. demonstrated statistically significantly better pain reduction using Senza compared with low‑frequency spinal cord stimulation (SCS), but that in De Andres et al. there was no statistically significant difference between the 2 treatments in this regard. The expert advisers explained that the low‑frequency SCS devices used as the comparator in both studies work in the same way as those used in standard clinical practice in the NHS. However, the response to low‑frequency SCS was lower than expected in De Andres et al., compared with both clinical experience and other trial results including Kapural et al. The external assessment centre (EAC) also highlighted that pain reduction was greater in Kapural et al. for both Senza and low‑frequency SCS compared with both treatment arms in De Andres et al.
4.2 The committee was concerned about the methodological quality of the De Andres et al. (2017) study, noting the conclusions of the 2 EAC reports about the reliability and robustness of the evidence. Although the committee noted the weaknesses in both randomised controlled trials, including the potential for bias and concerns about the relevance of the results to the NHS, it agreed with the EAC's conclusion that Senza is at least as effective as low‑frequency SCS in terms of relieving pain. It acknowledged that current studies are limited to 2 years' follow-up; a clinical expert explained that 3-year outcome data will soon be available, and that the ultimate intention is to collect 5-year follow-up data. The committee considered that long-term outcome data would be particularly important, given that Senza and other similar devices are used to treat a chronic condition and have a lifespan of at least 10 years. The committee concluded that, in view of these uncertainties, it would be beneficial for clinicians to routinely collect clinical and procedural outcome data on the use of SCS including Senza. It was encouraged to hear that the UK Neuromodulation Registry has well-established data collection arrangements to support the gathering of useful data.
4.3 People having low‑frequency SCS often experience paraesthesia (or tingling sensations), but this is not the case with high-frequency SCS (such as Senza). The experts explained that people may have paraesthesia throughout the use of low‑frequency SCS devices and that this can impair day-to-day living. For example, intense paraesthesia may be distracting enough to interrupt sleep or prevent tasks such as driving or operating machinery. However, the committee heard that some patients (usually those who have had low‑frequency SCS for a long time) find the presence of paraesthesia reassuring, because it confirms that the device is still working. The committee concluded that paraesthesia after SCS device implantation is an important issue that should be discussed with patients before choosing a device.
4.4 The committee noted that most of the higher quality evidence for the clinical benefits of Senza is in people who have chronic back or leg pain despite previous back surgery. The clinical experts agreed that this is the largest group of patients who are likely to benefit from Senza, but highlighted others who may benefit (for example, people for whom surgery is either not possible or unlikely to be successful and people with neuropathic pain of other causes including complex regional pain syndrome). However, the committee concluded that there is limited evidence to support the claimed benefits for Senza in these other patient groups. It noted that these patient groups are already covered by the recommendations in the NICE technology appraisal guidance on spinal cord stimulation. The committee also concluded that more evidence would be valuable about the potential role of Senza for neuropathic pain in patients who have not had previous back surgery. The committee was supportive of further research in these difficult circumstances, and would encourage SCS users to include patient data following all implantations in the UK Neuromodulation Registry.
4.6 The clinical experts explained that because paraesthesia mapping is not needed when using Senza, implantation procedure times may be shorter and more predictable compared with those for low‑frequency SCS devices. The committee was advised that, typically, 2 electrodes are used when implanting Senza compared with 1 electrode for low‑frequency SCS devices. The EAC explained that these factors had not been quantified in the published studies and so were not included in the cost modelling. The committee concluded that it is plausible that using Senza may allow for better planning of procedure times (thereby potentially increasing the number of procedures per operating list).
4.7 The clinical experts explained that when first adopting Senza in their services, the company provided trained experts to attend procedures and support clinicians until competence had been achieved. This was confirmed by the company representatives who attended the meetings.
4.8 The clinical experts also explained that there may be further time savings when using Senza at follow-up appointments because, in their experience, programming is easier and less time-consuming than with low‑frequency SCS devices.
4.9 Based on NHS Supply Chain purchase data, the committee concluded that the low‑frequency SCS devices most commonly used in the NHS are rechargeable. The clinical experts explained that although Senza is also rechargeable, it needs to be charged more often than most low‑frequency SCS devices (for 30 to 45 minutes each day). The committee concluded that the need for recharging is an important factor that should be discussed with patients before choosing a device.
4.10 The committee noted that the company's cost model replicated that used to inform the NICE technology appraisal guidance on spinal cord stimulation, and that the model has also been subjected to peer review before being published elsewhere. It agreed with the EAC that supplementation of the model with data from Van Buyten et al. (2017) was appropriate.
4.11 The committee noted that the model assumed a time horizon of 15 years. This is appropriate for a long-term condition, but clinical outcome data are currently limited to 2 years after implantation. Nonetheless, it noted the EAC's conclusions that the claimed lifespan of Senza is plausible (see the supplementary EAC documents for more details). The clinical experts also explained that they had seen no evidence in their own clinical practices to suggest that the effectiveness of Senza diminishes over time.
4.12 The committee noted the uncertainties in the cost model associated with the use of drug costs adjusted for inflation. The EAC explained that additional modelling involving attempts to more accurately estimate the cost of drug management in the relevant patient groups would be difficult.
4.13 Having acknowledged that the acquisition costs of Senza and the comparators were an important driver of the cost modelling results, the committee noted that these had also been adjusted for inflation from the cost model used to inform the NICE technology appraisal guidance on spinal cord stimulation. Acquisition costs in the model were assumed to be:
Senza: £16,648, with a lifespan of 10 years.
Non-rechargeable low‑frequency SCS device: £11,281, with a lifespan of 4 years.
Rechargeable low‑frequency SCS device: £17,422, with a lifespan of 10 years.
The EAC confirmed that these are an accurate reflection of current device costs.
4.14 The committee noted the results of the EAC's updated cost model (which included explantation data from Van Buyten et al. 2017), which showed that:
Over 15 years, compared with using a non-rechargeable low‑frequency SCS device, Senza is cost incurring by £351 per patient (£23.40 per year).
Over 15 years, compared with using a rechargeable low‑frequency SCS device, Senza is cost saving by £2,292 per patient (£152.80 per year).
The committee concluded that, despite the uncertainties in the cost model and the extrapolations made over the 15-year time horizon, it is unlikely that using Senza will incur additional overall costs compared with using low‑frequency SCS devices.