Prostate-specific antigen nadir concentration, hypertension and diabetes as risk factors for biochemical failure after permanent 125I seed brachytherapy for prostate cancer.

The aim of this study was to evaluate risk factors for biochemical failure (BF) following permanent prostate seed 125I brachytherapy for prostate cancer. The study reviewed the medical records of 607 patients with biopsy-proven prostate adenocarcinoma who were treated at Oulu University Hospital between 2001 and 2014. Clinical characteristics at diagnosis, treatment-related data and follow-up data were collected to identify potential risk factors for BF, which was defined using the Phoenix criteria [prostate-specific antigen (PSA) increase >2 µg/l from the PSA nadir concentration, which defined as the lowest PSA concentration observed after BT]. The median follow-up was 81 months. BF was detected in 117 (19.3%) patients. The PSA nadir concentration was associated with BF. The mean times to BF were 114 [95% confidence interval (CI): 112-116] and 55 (95% CI: 47-63) months for patients with PSA nadir concentrations <0.5 and ≥0.5 µg/l, respectively (P<0.001). Patients with underlying hypertension or diabetes tended to develop BF more rapidly. For patients without and with hypertension, the mean times to BF were 104 (95% CI: 100-107) and 98 (95% CI: 93-103) months, respectively (P=0.035). For patients without and with diabetes, the mean times to BF were 103 (95% CI: 100-106) and 89 (95% CI: 77-102) months, respectively (P=0.006). The overall survival and prostate cancer-specific survival rates were 90.3 and 98.0%, respectively. The mean overall survival and prostate-cancer specific survival times were 147 and 158 months, respectively. Therefore, PSA nadir level was identified as a clear risk factor for BF. In addition, BF tended to develop more rapidly among patients with underlying hypertension or diabetes. These risk factors should be considered, and individually tailored follow-up may be useful for identifying patients requiring more intense follow-up for early BF detection.