Secondary primary tumors following iodine-125 low-dose-rate brachytherapy for localized prostate cancer

Abstract Background Low-dose-rate brachytherapy with iodine-125 (LDR-BT) is an established curative radiation treatment modality for localized prostate cancer (PCa). This study aimed to evaluate the long-term incidence of secondary primary tumors (SPTs) following LDR-BT in Japanese patients with localized PCa and identify predictive factors associated with SPTs. Methods and materials We retrospectively reviewed the clinical records of 478 consecutive patients with localized PCa who underwent LDR-BT at the Gifu University Hospital. This study’s primary endpoint was SPTs incidence, including bladder and rectal/anal cancers. The secondary endpoint was the identification of risk factors for LDR-BT that predicted SPTs development. Results After a median follow-up period of 105 months, SPTs developed in 13 patients (2.7%). Bladder cancer and rectal/anal canal cancer were observed in seven (1.5%) and six (1.3%) patients, respectively. Multivariate analysis showed that a biologically effective dose (BED) ≥ 197 Gy was associated with increased risk of SPTs (hazard ratio 4.145; 95% confidence interval 1.108–15.498; p = 0.035). Conclusions The incidence of SPTs following LDR-BT was relatively low. In multivariate analysis, BED ≥ 197 Gy may be associated with an increased risk of SPT occurrence. Adequate tumor control can be achieved through appropriate radiation dose administration; carefully planned long-term follow-up may be beneficial for SPTs early detection.