Microwave tissue ablation for primary and secondary liver cancer

Abstract

Main issues for Medical Services Advisory Committee consideration -The clinical claims for the superiority of microwave tissue ablation (MTA) over radiofrequency ablation (RFA) made in the application are not supported by the evidence. -There is very little randomised controlled trial evidence for this intervention. -Much of the evidence included for this intervention uses historical controls; that is, institutions went from using RFA to using MTA, and then compared the experience of the MTA patients with the experience of earlier patients. This is likely to have important ramifications for the effectiveness of the intervention, as many other aspects of the treatment may also have changed in that time, such as chemotherapy, imaging, patient selection for ablation and surgery, and the equipment used to deliver the ablation. -Selection bias is also highly likely in most of the populations included in the evidence base, as most studies simply included patients seen in their institutions, and there was little discussion about who was excluded from analyses or how patients were selected for ablation. Moreover, in most studies, there was a lack of information relevant to prognosis, for example time since diagnosis, and these factors are likely to confound the results. -There does seem to be some evidence that MTA works better than RFA in more severe cases of cancer; however, given the problems with historical controls, the superior effectiveness may actually be due to improvements in other treatments, or indeed in patient selection for the treatment. -In patients with liver metastases, most of the identified evidence was excluded because patients underwent concomitant resection (meaning they were not ‘unresectable’ as described in the ‘Population’ component of the PICO criteria). It is likely that patients in this group, who have more complex disease, undergo a range of treatments, and finding evidence for just one of them in isolation will be difficult. -Despite the claims that MTA has quicker ablation time and fewer required sessions, there was little evidence available to support these claims.