Secondary cancers after intensity-modulated radiotherapy, brachytherapy and radical prostatectomy for the treatment of prostate cancer: incidence and cause-specific survival outcomes according to the initial treatment intervention

OBJECTIVE To report on the incidence of secondary malignancy (SM) development after external beam radiotherapy (EBRT) and brachytherapy (BT) for prostate cancer and to compare this with a cohort contemporaneously treated with radical prostatectomy (RP). MATERIALS AND METHODS Between 1998 and 2001, 2658 patients with localized prostate cancer were treated with RP (n= 1348), EBRT (n= 897) or BT (n= 413). Using the RP cohort as a control we compared the incidence of SMs, such as rectal or bladder cancers noted within the pelvis, and the incidence of extrapelvic SMs. RESULTS The 10-year SM-free survival for the RP, BT and EBRT cohorts were 89%, 87%, and 83%, respectively (RP vs EBRT, P= 0.002; RP vs BT, P= 0.37). The 10-year likelihoods for bladder or colorectal cancer SM development in the RP, BT and EBRT groups were 3%, 2% and 4%, respectively (P= 0.29). Multivariate analysis of predictors for development of all SMs showed that older age (P= 0.01) and history of smoking (P < 0.001) were significant predictors for the development of a SM, while treatment intervention was not found to be a significant variable. Among 243 patients who developed a SM, the 5-year likelihood of SM-related mortality among patients with SMs in the EBRT and BT groups was 43.7% and 15.6%, respectively, compared with 26.3% in the RP cohort; P= 0.052). CONCLUSIONS The incidence of SM after radiotherapy was not significantly different from that after RP when adjusted for patient age and smoking history. The incidence of bladder and rectal cancers was low for both EBRT- and BT-treated patients. Among patients who developed a SM, the likelihood of mortality related to the SM was not significantly different among the treatment cohorts.