RESUMO
AIM: To illustrate and stress the role of the dose volume relationship in the risk of radiation induced rectal complications. METHODS: With different techniques of irradiation like contact x ray therapy, Iridium implant, external beam irradiation, intra operative electrontherapy, it is possible to irradiate different volumes from few centicubes to liters. RESULTS: The data from the literature clearly demonstrate that high doses can be given safely in small volumes, but that doses of 50 Gy or more in large volumes are dangerous. The irradiation of the whole pelvis through two antero posterior (AP - PA) fields ecompassing more than 4 liters should not be recommended. Other classical risk factors must be taken into account when planning the treatment. Previous surgery, obesity, diabetus, collagen disease, combined chemotherapy, all these factors can lead to a modification of the irradiation technique. CONCLUSIONS: A perfect technique of irradiation is mandatory to achieve the best therapeutic ratio when treating rectal cancer. To avoid severe complications the dose must be closely adapted to the irradiated volume.
