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

The aim of this study was to evaluate risk factors for biochemical failure (BF) following permanent prostate seed I 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.