Oncological outcomes of I125low dose brachytherapy in localized prostate cancer

Low-dose rate (LDR) prostate brachytherapy is a recommended treatment of localized prostate cancer in current guidelines. The study aimed to determine biochemical relapse-free survival (BRFS) in patients treated with dynamic real-time low-dose rate (LDR) brachytherapy using Iodine 125 (I125).

We retrospectively reviewed 499 patients with localized prostate cancer treated with I125 LDR real-time brachytherapy between 2003 and 2021. The mean patient age was 65 years (range: 45-84 years). Based on the National Comprehensive Cancer Network (NCCN) risk classification, 230 patients (46.1%) were categorized as low risk, 235 (47.1%) as intermediate risk, and 34 (6.8%) as high risk. Gleason scores were distributed as follows: 3+3 in 283 cases (56.7%), 3+4 in 157 cases (31.5%), 4+3 in 46 cases (9.2%), and 4+4 in 13 cases (2.6%). The mean follow-up was 70.5 months.

Tumor relapse was observed in 47 patients (9.4%) over a mean follow-up period of 6.26 years (SD 4.16). Local recurrence within the prostate occurred in 20 cases (4%). Patients with nadir PSA <0.2 ng/mL at 5 years of follow-up had a significantly lower incidence of tumor recurrence (3%) compared to those with a nadir PSA >0.2 ng/mL (21.9%) (p = 0.0001). Biochemical relapse-free (BRFS) rates at 5, 10 and 15 years were 96%, 91.5% and 88.9%, respectively. When stratified by NCCCN risk groups, 5-year BRFS was 96% in low risk, 98% in intermediate risk and 85% in high risk patients (p = 0.003). In multivariate analysis, only age at the time of brachytherapy (p = 0.009), initial PSA (p = 0.007) and Gleason grade (p = 0.007) were significantly associated with tumor recurrence. Cancer-specific survival and overall survival were 99.8% and 98.0%, respectively.

LDR with I125 has excellent long-term oncological outcomes for patients with low and intermediate-risk prostate cancer, in particular, patients achieving a nadir PSA <0.2 ng/mL at 5 years post-treatment.