Does rectal cancer shrinkage induced by preoperative radio(chemo)therapy increase the likelihood of anterior resection? A systematic review of randomised trials

Background and purposeAccording to common conviction rectal tumour shrinkage after preoperative radio(chemo)therapy increases the likelihood of anterior resection (AR). In order to verify this belief, we performed a systematic review of randomised trials.Patients and methodsWe identified 10 randomised trials encompassing altogether 4596 patients in whom preoperative radio(chemo)therapy resulted in tumour shrinkage in the experimental arm as compared to the control arm.ResultsTumour shrinkage observed in the experimental groups did not result in a statistically significant higher ARs rate in any study when we performed an analysis of all the randomised cases. Subgroups of patients considered to be candidates for abdominoperineal resection before randomisation were identified in three trials. A statistically significantly higher rate of ARs was demonstrated in the experimental arm of the CAO/ARO/AIO 94 study. However, in that study, sphincter preservation was a secondary endpoint and some features of the trial may bias the estimation of the effect. The benefit of sphincter preservation was not confirmed by subgroup analyses performed in the Lyon R90-01 study and in the Polish study, which were originally designed to evaluate the sphincter preservation issue.ConclusionThe body of evidence gathered from randomised trials does not support the concept of a beneficial effect of preoperative radiotherapy on the ARs rate.