Investigation of the Effect of Fractionated Regimes of Irradiation in Normal Tissues

Abstract

Different fractionated regimes of irradiation used in the post-operative treatment of carcinoma of the stomach have been assessed by their effect on normal tissue; the mucosa of the small intestine has been used for this purpose. A regime consisting of a few large fractions was found to cause excessive damage through their inopportune spacing. Treatment by an increased number of smaller fractions was associated with evidence of repair of the normal tissue damage despite continued irradiation. The implications of this with respect to the radiation effect in tumors are discussed. An experimental fractiona-tion regime incorporating a few large fractions but avoiding excessive immediate normal tissue damage by suitable spacing of the fractions is reported. Serial peroral jejunal biopsies were obtained prior to and during the course of irradiation so that each treatment was given only after evidence of repair of the damage resulting from the previous dose had been observed. By this means a normal mucosal pattern was preserved immediately following treatment and was still present 18 mon. later, though this time interval is not considered adequate to exclude the development of later radiation damage.