Correlation of radiotherapeutic parameters and treatment related morbidity--analysis of RTOG Study 77-06

The current report is an updated and detailed analysis of treatment related morbidity in RTOG 77-06, a Phase III randomized study comparing prostatic irradiation versus pelvic irradiation followed by a prostatic boost, in patients with Stage A2 and B carcinoma of the prostate without evidence of nodal involvement. A total of 453 analyzable cases were accrued from 1978 to 1983, when the study was closed. All cases of treatment related morbidity were classified as to severity (using a clinical severity grading system). The data were then correlated with a number of radiotherapeutic parameters including treatment volumes (fields), doses, and techniques. Overall, pelvic irradiation, compared to prostate irradiation only, was not associated with a significantly increased incidence of treatment related morbidity. Within the range of pelvic doses used in this study a significant dose effect could not be detected. Total doses to the prostate of more than 7000 cGy were associated with an increased risk of rectal bleeding. Certain treatment techniques, (AP/PA irradiation of the pelvic lymphatics) were associated with an increased incidence of bowel complications.