Cancer du rectum et chimiothérapie adjuvante : quelles conclusions ?

Abstract

Adenocarcinoma of the rectum represents about a third of cases of colorectal cancer, with an annual incidence of 12,000 cases in France. On the contrary of colon cancer, the benefice of adjuvant chemotherapy in rectal cancer has not been definitively proved, more because this question was assessed in few recent studies than because negative results. Preoperative radiochemotherapy is now the reference treatment for mid and lower rectal cancers, and allow to increase the local control without improvement of progression free survival and overall survival. The data of the “historical studies” of adjuvant treatment in rectal cancer published before 1990, of the meta-analysis of adjuvant trials in rectal cancer and of the QUASAR study suggest that adjuvant chemotherapy with fluoropyrimidines (intravenous or oral), in absence of pre-operative treatment, decrease the risk of metastatic relapse after curative surgery for a rectal cancer of stage II or III. This benefice seems similar to the one observed in colon cancer. In the EORTC radiotherapy group trial 22921, an adjuvant chemotherapy with 5-fluorouracil and low dose of leucovorin was not associated with a significantly improvement of overall survival but, despite the fact that only 42.9% of patients received all planed cycles, the progression free survival was increased (not significantly) in groups receiving adjuvant chemotherapy. The French recommendations are to discuss the indication of adjuvant chemotherapy by fluoropyrimidines in cases of stage III rectal cancer on histopathologic reports and no chemotherapy in case of stade II. Despite the fact that none study have assessed a combination of fluoropyrimidines and oxaliplatin in adjuvant setting in rectal cancer, like in colon cancer, the Folfox4, modified Folfox6 or Xelox regimens are valid options in stage III (experts opinion). In cases of pathologic complete remission or in absence of involved nodes, the benefice of adjuvant chemotherapy is not assessed. In all cases, the decision of adjuvant chemotherapy has to be taken during a multidisciplinary meeting. The interest of a combination of fluoropyrimidine and oxaliplatin is assessed in currently adjuvant trials (PETTAC-6 and CAO/ARO/AIO-04), and future trials will assess the interest of neoadjuvant chemotherapy.