A Systematic Overview of Radiation Therapy Effects in Rectal Cancer

Abstract

A systematic review of radiation therapy trials in several tumour types was performed by The Swedish Council of Technology Assessment in Health Care (SBU). The procedures for evaluation of the scientific literature are described separately (Acta Oncol 2003; 42: 357-365). This synthesis of the literature on radiation therapy for rectal cancer is based on data from 42 randomized trials and 3 meta-analyses. Moreover, data from 36 prospective studies, 7 retrospective studies and 17 other articles were used. A total of 131 scientific articles are included, involving 25 351 patients. The results were compared with those of a similar overview from 1996 including 15 042 patients. The conclusions reached can be summarized thus: The results after rectal cancer surgery have improved during the past decade. It is likely that local failure rates after 5 years of follow-up at hospitals adopting the TME-concept (TME = total mesorectal excision) have decreased from about 28% to 10-15%. Preoperative radiotherapy at biological effective doses above 30 Gy decreases the relative risk of a local failure by more than half (50-70%). Postoperative radiotherapy decreases the risk by 30-40% at doses that generally are higher than those used preoperatively. There is strong evidence that preoperative radiotherapy is more effective than postoperative. There is moderate evidence that preoperative radiotherapy significantly decreases the local failure rate (from 8% to 2% after 2 years) also with TME. There is strong evidence that preoperative radiotherapy improves survival (by about 10%). There is no evidence that postoperative radiotherapy improves survival. There is some indication that survival is prolonged when postoperative radiotherapy is combined with concomitant chemotherapy. Preoperative radiotherapy at adequate doses can be given with low acute toxicity. Higher, and unacceptable acute toxicity has been seen in some preoperative radiotherapy trials using suboptimal techniques. Postoperative radiotherapy can also be given with acceptable acute toxicity. The long-term consequences of radiotherapy appear to be limited with adequate radiation techniques, although they have been less extensively studied. Longer follow-up periods are needed before firm conclusions can be drawn. Peroperative radiotherapy, preferably preoperative since it is more effective, is routinely recommended for most patients with rectal cancer since it can substantially decrease the risk of a local failure and increases survival. In a primarily non-resectable tumour, preoperative radiotherapy can cause tumour regression allowing subsequent radical surgery. This therapy is routinely indicated. Whether radiochemotherapy is more efficient than radiotherapy alone is not clear, since the results of four small randomized trials are partly conflicting. Preoperative radiotherapy, frequently combined with chemotherapy, has been used to increase the chances of sphincter-preserving surgery in low-lying tumours. The literature is inconclusive with respect to how frequently this occurs. Radiotherapy frequently produces symptom relief in patients with rectal cancer not amendable to surgery.