Radiation therapy in prostate cancer: whole pelvis with prostate boost or small field to prostate?

The purpose of this retrospective study is to identify prostate cancer patients who would benefit from pelvic nodes irradiation (whole pelvis) as opposed to the small-field irradiation to the prostate only. Between 1975 and 1983, 126 patients were treated by whole pelvis (4,600-5,000 cGY) with prostate boost (2,000 cGY) radiation (WP + P). Median follow-up was six years and six months. Comparison was made with historic control of 116 patients irradiated at the same institutions between 1971 and 1977 by small field to the prostate (P) to a dose of 7,000-7,500 cGY. There was a significant five-year survival improvement in the current WP + P radiation in Stage C (72% vs 40%, p = 0.0004) and Stage B (92% vs 70%, p = 0.025) but not in Stage A2 patients. However, WP + P radiation significantly improved disease-free survival (DFS) in only well and moderately but not in poorly differentiated carcinoma with a combined well and moderately differentiated five-year DFS of 63 percent compared with the 45 percent in P radiation (p = 0.0228). Local tumor control was significantly improved in WP + P radiation in only Stage C cancers with their local recurrence rate 16 percent as compared with the 34 percent in P radiation (p = 0.0172). Although acute radiation reactions were more frequent in WP + P than P radiation (61% vs 41%, p = 0.0022), chronic radiation morbidity in both series were similar. Thus, whole pelvis with prostate boost radiation should be utilized in Stage B and Stage C cancers as this has shown to increase the survival of the patient without increasing chronic radiation morbidity.