Problems of the Irradiation of the Pelvis Cancers in Obese Patients

Abstract

The irradiation of the pelvis in obese patients meets biological and technical difficulties sometimes considered insuperable. Chiefly when it is necessary to irradiate a very large volume of tissues (for instance, in the case of the irradiation of the pelvis in uterus and ovary cancers) radiotherapy is sometimes considered unsuitable because of considerations concerning the integral dose to be reached, the acute or late reactions expected, difficulties in the choice of the irradiation technique and the execution itself of the therapy. Actually the irradiation of the pelvis in obese patients is clinically possible: it has been performed without complications by the author up to integral doses of 6 × 107 grads in 50 days. The most important problem is the correct choice of treatment technique: when Co 60 gamma rays are employed, obese patients must be irradiated by means of moving beam techniques. The author brings into evidence that obese women, bearing uterus carcinomas, can be irradiated by means of biaxial pendular techniques, employing the same parameters (field at axis, arc width, position of the axis) as in normal subjects. In effect the pelvis in obese subjects is in the center of the corporal section, as in thin subjects. The shape of isodoses in pendular axial irradiations, for Co 60, does not dipend from the dimensions of the body irradiated. The properties of high voltage moving beam radiotherapy turn to the advantage of obese patients. Technical difficulties, which are not negligible, may always be overcome with proper devise.