Late genitourinary and gastrointestinal toxicity and radiation-induced second primary cancers in patients treated with low-dose-rate brachytherapy.

OBJECTIVES

To evaluate late genitourinary (GU) and gastrointestinal (GI) toxicities and radiation-induced second primary cancers (RISPCs) in patients who received low-dose-rate brachytherapy (LDR-BT) with or without external beam radiotherapy for prostate cancer.

METHODS

This retrospective study included 897 consecutive patients who received LDR-BT between July 2004 and July 2015 in our institution. Adverse events and the incidence of second primary cancers were evaluated at 1, 3, 6, 12, 18, 24, 30, 36, 48, 54, and 60 mo after LDR-BT and then once a year. Related factors to ≥grade 2 (G2) toxicity were evaluated using the Cox proportional-hazards model.

RESULTS

The median follow-up time was 85.2 (interquartile range: 66.8-111.3) mo. The cumulative incidence rates of ≥G2 GU toxicity at 5 and 10 yrs after LDR-BT were 11.2% and 14.7%, respectively. The International Prostate Symptom Score before LDR-BT (continuous) (hazard ratio [HR]: 1.03), no neoadjuvant androgen deprivation therapy (HR: 1.69), and combination external beam radiotherapy (HR: 3.30) were risk factors related to the incidence of ≥G2 GU toxicity. The cumulative incidence rates of ≥G2 GI toxicity at 5 and 10 yrs after LDR-BT were 3.3% and 3.3%, respectively. Age (continuous) (HR: 1.09), body mass index (continuous) (HR: 0.87), and rectum V100 (continuous) (HR: 1.64) were risk factors related to ≥G2 GI toxicity. A total of 12 (1.3%) patients developed metachronous RISPCs (bladder cancer: 9; rectal cancer: 3).

CONCLUSION

The incidence rates of late GU and GI toxicities and RISPCs after LDR-BT were low.