THE RATE OF SECONDARY MALIGNANCIES AFTER RADICAL PROSTATECTOMY VERSUS EXTERNAL BEAM RADIATION THERAPY FOR LOCALIZED PROSTATE CANCER: A POPULATION-BASED STUDY ON 17,845 PATIENTS

Purpose: External-beam radiation therapy (EBRT) may predispose to secondary malignancies that include bladder cancer (BCa), rectal cancer (RCa), and lung cancer (LCa). We tested this hypothesis in a large French Canadian population-based cohort of prostate cancer patients. Methods and Materials: Overall, 8,455 radical prostatectomy (RP) and 9,390 EBRT patients treated between 1983 and 2003 were assessed with Kaplan-Meier and Cox regression analyses. Three endpoints were examined: (1) diagnosis of secondary BCa, (2) LCa, or (3) RCa. Covariates included age, Charlson comorbidity index, and year of treatment. Results: In multivariable analyses that relied on incident cases diagnosed 60 months or later after RP or EBRT, the rates of BCa (hazard ratio [HR], 1.4; p = 0.02), LCa (HR, 2.0; p = 0.004), and RCa (HR 2.1; p<0.001) were significantly higher in the EBRT group. When incident cases diagnosed 120 months or later after RP or EBRT were considered, only the rates of RCa (hazard ratio 2.2; p = 0.003) were significantly higher in the EBRT group. In both analyses, the absolute differences in incident rates ranged from 0.7 to 5.2% and the number needed to harm (where harm equaled secondary malignancies) ranged from 111 to 19, if EBRT was used instead of RP. Conclusions: EBRT may predispose to clinically meaningfully higher rates of secondary BCa, LCa and RCa. These rates should be included in informed consent consideration. (C) 2010 Elsevier Inc.