Use of placebo controls in the evaluation of surgery: a systematic review


Dr Karolina Wartolowska a researcher in Professor Carr's research group has recently published a review on surgical randomised clinical trials.

Below is a synopsis on this research penned by Dr Wartolowska:

"Surgical randomised clinical trials are rare and surgical trials with a placebo control are very uncommon. There are several reasons for that but the main concerns are about their benefits and harms. So far, there have been no systematic reviews of the existing trials. We wanted to investigate whether placebo control should be used in the evaluation of surgical interventions, and to do so, we set out to analyse all randomised clinical trials that compared surgical interventions with placebo and were published as full-text papers. We wanted to make the review as comprehensive as possible therefore we did not limit our search to any particular condition, patient group, intervention, or type of outcome. We assessed improvement in each arm and the superiority of surgery using the outcomes reported by the authors of each study. Moreover, we used data reported in each trial to calculate the odds ratio or effect size for improvement in the surgical arm compared with the placebo arm. We estimated the harms using the reported severity of adverse events and their relevance to the trial interventions.

Our study, published in BMJ in May had several interesting findings. Firstly, performing a meta-analysis of the effects in each arm was not possible as the identified 53 trials were very heterogeneous and differed in the studied patient population, type of intervention, surgical technique, type of anaesthesia and the main outcomes. Secondly, adverse events were not reported in sufficient detail to allow for any quantitative analysis and often the trial’s authors did not specify whether the event occurred in the surgical or the placebo group, and whether it was related to the investigated intervention or the severity of the condition. Thirdly, the magnitude of placebo effect could not be estimated owing to a lack of a non-treatment control group in all but one trial. What is interesting, the existing trials investigated only less invasive procedures that did not involve laparotomy, thoracotomy, craniotomy, or extensive tissue dissection. In many of these studies, significant improvement was present in both arms, and in half of the trials the effect of placebo was no different from surgery, suggesting that the clinical improvement in a trial may be a result of factors other than the actual surgery. In general, placebo controlled surgical trials were not free from adverse events but harms were minimised and the placebo arm was generally safer than the surgery arm.

This review has demonstrated that placebo controlled trials are a powerful, feasible way of investigating the efficacy of surgical procedures. They should be considered for selected procedures because without such studies ineffective treatment may continue unchallenged. "