ESTRO 2024 - Abstract Book

S411

Brachytherapy - Urology

ESTRO 2024

the available data in 2016. The aim of this study is to compare two schedules of HDR-BT in term of efficacy and toxicity.

Material/Methods:

A retrospective analysis of patients treated with HDR-BT due to prostate cancer in the years 2008 – 2018 was performed. All patients were treated with perineal interstitial HDR-BT under epidural or general anaesthesia in the lithotomy position. Schedule one (“3x11 Gy”; 2008– 2016) consisted of three fractions of 11 Gy delivered within 28 days, while schedule two (“2x13 Gy”; 2016– present) was two fractions of 13 Gy delivered within 7 – 14 days. Biochemical recurrence was defined according to Phoenix criteria. Biochemical control (BC), local control (LC), distant metastasis-free survival (DMFS) and disease-free survival (DFS) were calculated. Toxicity was assessed according to CTCAE v5.0. The Kaplan-Meier estimator, log-rank test and Mann – Whitney U test were used in statistical analysis. Two hundred twenty-seven patients were enrolled in this analysis. Median age was 65 years (range: 39 – 84 years). Median follow-up was 83 months (range: 18 – 185). Median PSA max at primary diagnosis was 7.81 ng/mL (range: 0.13 – 22.03 ng/mL). ISUP grade 1 was diagnosed in 71.0% of patients, 2 – in 21.6%, 3 – in 7.0%, and in 1 patient (0.4%), it was not determined. The comparison of groups with different fractionations revealed that in the “2x13 Gy” group the Gleason score was significantly higher (p=0.0000), and significantly more patients were in intermediate or high-risk groups (p=0.002). In the “3x11 Gy” group, there were 95 patients. Median age was 64 years (range: 39– 79 years). Median follow-up was 114 months (range: 102 – 185 months). Median PSA max at primary diagnosis was 7.57 ng/mL (range: 1.87 – 18.23 ng/mL). ISUP grade 1 was diagnosed in 83.2% of patients, 2 – in 12.6%, 3 – in 3.2%, and in 1 patient (1.0%), it was not determined. In the “2x13 Gy” group, there were 132 patients. Median age was 65 years (range: 50– 84 years). Median follow-up was 75 months (range: 18 – 90 months). Median PSA max at the primary diagnosis was 8.1 ng/mL (range: 0.13 – 22.03 ng/mL). ISUP grade 1 was diagnosed in 62.1% of patients, 2 – in 28.0%, and 3 – in 9.9%. In the whole group, median BC, LC, DMFS and DFS were not reached. Five- and 10-year BC was 87.2% and 83.8%, respectively; 5- and 10-year LC was 91.2% and 85.9%, respectively; 5- and 10-year DMFS was 95.6% and 94.4%, respectively; and 5- and 10-year DFS was 88.1% and 82.1%, respectively. There were no statistically significant differences in BC (p=0.2), LC (p=0.6), DMFS (p=0.4) and DFS (p=0.5) between the “3x11 Gy” and “2x13 Gy” groups. There were no statistically significant differences in BC (p=0.5), LC (p=0.2), DMFS (p=0.4) and DFS (p=0.2) between risk groups. Within the 1st month after HDR- BT, gastrointestinal (GI) toxicity was significantly higher in the “3x11 Gy” group (p=0.04), while genitourinary (GU) toxicity was significantly higher in the “2x13 Gy” group (p=0.01). In the “3x11 Gy” group, there was one patient with acute G3 proctitis and one with acute G3 haematuria, whereas there were no >G2 toxicities in the “2x13 Gy” group. In the “3x11 Gy” group, the cumulative incidence of GU and GI late toxicity was 15.8% and 1.0%, respectively, while in the “2x13 Gy” it was 32.6% and 0%, respectively. On the last follow -up, the GU toxicity was significantly higher in the “2x13 Gy” group (p=0.004). There was one patient with G3 diarrhoea, one with Results: