Second cancer following radical prostate cancer treatment.

16Background: We estimated second cancer (SC) risk following radical prostate cancer (PC) treatment and evaluated if the risk was influenced by treatment. Methods: We analyzed data from the Cancer Registry of Norway on all patients with PC (first cancer diagnosis) from 1997-2014. Standardized incidence ratios (SIRs) for SC were calculated. Subdistribution hazard ratios (SHRs) were estimated in treatment groups (prostatectomy (RP) reference). Results: Median follow-up in 24155 radically treated patients was 6 and 4 years in the external beam radiotherapy (EBRT) and RP-groups, respectively. SC-incidence was indifferent from that of the reference population in 24155 radically treated patients, higher following EBRT, SIR 1.06(1.01-1.12), and lower following RP, SIR 0.91(0.84-0.98). EBRT-patients had higher rectal and urinary bladder cancer incidences. Compared to RP, the EBRT-patients had a 38 % higher risk of any SC. Respective figures for rectal, urinary bladder and lung cancer: 72, 38, and 113%. Conclusion...