[Rectal cancer: need for radiotherapy in determining the treatment plan].

Postoperative radiotherapy is highly effective in the prevention of local recurrence in rectal cancer. Nevertheless, the results remain disappointing for Locally Advanced Rectal Cancer. New approaches include introduction of chemotherapy to postoperative radiotherapy or combined radiotherapeutic treatment with preoperative irradiation, surgery and intraoperative irradiation, along with elective postoperative treatment in function of surgical and pathological data. Based on recent advances in radiobiology we are able to modify treatment parameters to enhance efficacy without increasing the toxicity. The reduction of dose per fraction, the application of radiosensitizers, the optimal protection of healthy tissue will increase the therapeutic ratio while keeping results constant or even reduce the incidence of local failure.