[Radiotherapy in cancer of the rectum]

The response of adenocarcinoma of rectum to radiotherapy is dependent on the use of irradiation techniques that ensure a sufficient dose be applied to the tumor without exceeding tolerance limits of pelvic tissues. This has been clearly demonstrated by results of contact radiotherapy over the last 30 years or so. Doses of about 100 Gy provide local control in 90% of cases and a 5 year survival rate of 80% in patients with highly selected tumors. For several years now, contact radiotherapy has been associated with external irradiation and iridium therapy with resulting sterilization of T2 and even T3 or N1 tumors in inoperable cases. Endorectal ultrasound imaging is essential for selecting those patients requiring radiotherapy alone and for evaluating the results, but in more than 90% of patients, surgery remains basic treatment for cancer of rectum. The incidence of local recurrence, very difficult to treat, is non negligible, however, but combining radiotherapy with surgery has been shown to reduce the rate of by 50%. Opinions differ on the relative efficacy of pre- or post-operative radiotherapy, but tolerance to this treatment is good in both cases if the technique used limits radiation to the posterior pelvis. Results of a Swedish randomized trial demonstrated greater efficacy for pre-operative radiotherapy for controlling local spread. Meta analysis showed that irradiation produces a definite gain in local control with a resulting gain in survival of about 5 to 10%. In the USA, chemotherapy based on 5 FU combined with post-operative radiotherapy was equally favorable in terms of survival. Pre-operative radiotherapy may also increase the chance of conservation of the sphincter. Although numerous points concerning chronology and mode of treatment remain open to discussion, a combination of radiotherapy and surgery now appears as standard treatment for rectal cancer.