Secondary malignancies following low-dose-rate brachytherapy for prostate cancer in a single institution.

142Background: Low-dose-rate brachytherapy (BT) is the internal radiation therapy for non-metastatic prostate cancer by implanting radioactive isotope Iodine 125 into the prostate. The carcinogenetic effect of radiation for the treatment of cancer has been proven during the last decades. However, few studies have been reported about brachytherapy-induced secondary malignancies. In this study, we assessed the BT-induced secondary malignancies in our institution. Methods: We reviewed 487 patients treated with low-dose-rate BT from 2006 to 2016 in our hospital. We checked the occurrence of metachronous malignancies (MM) in all the patients and examined the features of MM including the number, organ sites, histology, period from BT to the occurrence, and analyzed whether the features meet the criteria of radiation-induced malignancies. We also examined the relationship between the BT-related radiation doses and the occurrence of MM. We adopted the criteria of radiation-induced cancer proposed by Sakai et al i...