Long Term Second Malignancies in Prostate Cancer Patients Treated with Low-Dose-Rate Brachytherapy and Radical Prostatectomy.

Second malignancy is a rare but potentially lethal event after prostate brachytherapy, but data remain scarce on its long-term risk. The objective of this study is to estimate the number of pelvic second malignancies following brachytherapy compared to prostatectomy (RP).

Retrospective review of patients treated with low dose 125I brachytherapy and prostatectomy in British Columbia from 1999 to 2010. Kaplan Meier (KM) estimates for pelvic (bladder and rectum), invasive pelvic, any second malignancy and death from any second malignancy were assessed. Cox multivariable analyses were performed adjusting for initial treatment type, age, post RP adjuvant/salvage EBRT status, and smoking history.

Two thousand three hndred seventy-eight brachytherapy and 9089 prostatectomy patients were included. Median age was 66 years (IQR 61-71) and 63 years (IQR 58-67), respectively. Median follow-up time to event or censured was 14 years (IQR 11.5-17.3). The KM estimates for pelvic second malignancy at 15 and 20 years were 6.4% and 9.8% after brachytherapy, and 3.2% and 4.2% after prostatectomy. Time to any second malignancy and time to death from any second malignancy were not significantly different (P > .05). On Cox-multivariable analysis, brachytherapy, compared to surgery, was an independent factor for pelvic (HR 1.81 [95% CI 1.45-2.26], P < .001) and invasive pelvic second malignancy (HR 2.13 [95% CI 1.61-2.83], P < .001). Increased age and smoking were also associated with higher estimates of events (P < .001).

After adjustment for age, post RP adjuvant/salvage EBRT status and smoking status, numerically higher long-term HRs of pelvic and invasive pelvic second malignancy in patients treated with brachytherapy compared to radical prostatectomy were noted.

The Journal of urology. 2024 Apr 11 [Epub ahead of print]

Marie-Pier St-Laurent, George Acland, Sarah N Hamilton, Jeremy Hamm, Katherine Sunderland, Peter C Black, Michael McKenzie, Mira Keyes, Stacy Miller, Martin E Gleave, Scott Tyldesley

Department of Urologic Sciences, University of British Columbia, Vancouver, British Columbia, Canada., Christchurch Hospital, Christchurch, New Zealand., Department of Radiation Oncology, British Columbia Cancer Agency Vancouver Centre, Vancouver, British Columbia, Canada., Data and Analytics, BC Cancer, Vancouver, British Columbia, Canada., Department of Radiation Oncology, BC Cancer-Centre for the North, Prince George, British Columbia, Canada.