Marieke van Son

89 MRI-GUIDED ULTRAFOCAL SALVAGE HDR-BRACHYTHERAPY clinically relevant change. 12 Time-to-event analyses were performed using the Kaplan Meier-estimator, with no competing events between different outcomes. An explor- ative risk factor analysis for biochemical failure was performed with a univariable Cox regression for age, American Joint Committee on Cancer(AJCC) grade group, T-stage, PSA, PSADT and CTV size. Based on the resulting risk factors, we divided the cohort into groups of low and high risk of treatment failure to visualize the effect on biochemical disease-free survival (BDFS) curves. Analyses were performed with R statistical software (version 3.5.1; the R foundation for Statistical Computing, Vienna, Austria) and IBM SPSS statistics (version 25.0). RESULTS Baseline patient and tumor characteristics are displayed in Table 1. Median follow-up was 31 months (range 13 – 58 months). Table 1 – Baseline characteristics No. patients (%) / median (range) Total 50 Primary setting iPSA 13 ng/ml (2.1 – 140) Clinical T-stage T1c T2a T2b T3a 26 (52%) 10 (20%) 1 (2%) 13 (26%) Gleason grade group 1 2 3 4 5 Missing 33 (66%) 6 (12%) 2 (4%) 3 (6%) 3 (6%) 3 (6%) AJCC prognostic stage group Stage I Stage IIA Stage IIB Stage IIC Missing 31 (62%) 4 (8%) 9 (18%) 3 (6%) 3 (6%) Radiation treatment EBRT (70-78Gy) LDR-BT (145 Gy) 25 (50%) 25 (50%) 5