Radiation-associated morbidity in patients undergoing small-field external beam irradiation for prostate cancer

To quantify complication rates after small-field external beam irradiation for adenocarcinoma of the prostate in a uniformly treated patient population with long follow-up using a simple tool designed to identify subtle treatment-related side effects; and to identify clinical and technical variables associated with increased morbidity after irradiation.

A total of 441 patients with nonmetastatic adenocarcinoma of the prostate treated at the Joint Center for Radiation Therapy between 1985 and 1989 were eligible for analysis. Gastrointestinal, genitourinary, and sexual function were assessed retrospectively using a patient self-scoring, five-grade toxicity scale. Seven clinical and 15 technical variables were recorded for each patient. The association between the clinical and technical variables and rectal, bladder, and sexual side effects was examined. The 375 patients who received small-field (<12.5 x 12.5-cm) external beam irradiation via a four-field box on a 6-MV (n = 74, or 20% of patients), 8-MV (n = 140, or 37%), or 15-MV (n = 161, or 43%) linear accelerator form the basis for the study. Ninety-one percent of patients received treatment with 1.8-2.0 Gy fractions to a delivered dose of at least 66 Gy. Follow-up was complete through 62 months in living patients, with five (1%) of the entire group lost to follow-up.

A total of 137 of 354 evaluable patients (39%) reported rectal complications after treatment; however, 20 patients(6%) had heme-positive stools as their only symptom and 66 (19%) had mild symptoms not requiring treatment. Only 14% of the entire group required intervention. Of 356 patients, 117 (33%) evaluable for bladder complications developed genitourinary changes: In 14 patients (4%) asymptomatic hematuria occurred, 71 (20%) had mild symptoms not requiring treatment, and 32 (9%) required treatment. Of the 171 patients who were potent prior to radiation, 106 (62%) reported impotence after treatment. No statistically significant association was identified between any clinical or technical variables (including machine energy) assessed and complications.

In this retrospective review, treatment-related bowel and bladder side effects were not identified in the majority of patients despite the use of a grading system designed to identify subtle changes. Impotence, however, was common. Although pretreatment clinical characteristics varied among patients, they could not be used to predict the subsequent development of complications. The only treatment-related characteristic that varied in this study was machine energy, which did not correlate with complications.