To identify predictors of outcomes in patients with localized prostate cancer treated with iodine-125 brachytherapy in a longitudinal uncontrolled study. Between 2000 and 2011, 560 histologically confirmed patients were treated with brachytherapy of whom 305 with a parts per thousand yen24-month follow-up and localized tumor were evaluated after exclusion of those locally advanced and under androgen ablation. Patients' mean age was 63.93 years (44-88), mean pretreatment prostate-specific antigen (PSA) was 6.34 ng/mL (0.67-33.09), overall median follow-up was 75.35 months (24-158.37), biochemical recurrence occurred in 17 patients (5.57 %), cancer-specific survival was 100 %, and overall survival was 98.03 %. At multivariate analyses, only PSA-nadir at 1 year and age were related to disease-free survival: To each unit of PSA-nadir, the risk increases 87.3 %-OR 1.87 (p < 0.001; 95 % CI 1.31-2.67), and risk was 4.7 times higher for those under 50 years (vs. > 70)-OR 4.69 (p = 0.04; 95 % CI 1.39-18.47). Best cutoff for PSA-nadir at one year was 0.285 (AUC = 0.78; p < 0.001; 95 % CI 0.68-0.89). Kaplan-Meier analysis confirmed PSA-nadir (p < 0.001) as prognostic, while D'Amico's classification failed (p = 0.24). No grade 3 or 4 complication was reported, and only 31.4 % of patients had grade 2 urinary or rectal toxicity. PSA bounce a parts per thousand yen0.4 ng/mL occurred in 18.4 % with no impact on biochemical recurrence. Half (50.49 %) of patients in the scenario of localized prostate cancer treated with iodine-125 brachytherapy reach PSA-nadir at 1 year < 0.285, recognized as a key independent prognostic factor. [Receiver Operating Characteristic curve analysis for PSA-nadir at 1 year].323753759Instituto do Radium de Campinas (IRC), Campinas, SP, Brazil