ESTRO 2023 - Abstract Book

S519

Sunday 14 May 2023

ESTRO 2023

Salvage high-dose-rate brachytherapy (sHDR-BT) is an efficient option administered for relapsing prostate cancer patients in our department since 2008. We decided to shorten and intensify our schedule with an equivalent total dose based on the available data in 2016. The aim is to compare two schedules of sHDR-BT in terms of efficacy. Materials and Methods A retrospective analysis of patients treated with sHDR-BT due to local recurrence (LR) of prostate cancer. All patients were treated with perineal interstitial HDR-BT under epidural or general anaesthesia in the lithotomy position. Schedule one (“3x10 Gy”; 2008–2016) consisted of three fractions of 10 Gy in 28 days, while schedule two (“2x13 Gy”; 2016–present) was two fractions of 13 Gy in 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. The Kaplan- Meier estimator, log-rank test and Mann–Whitney U test were used in statistical analysis. Results Two hundred thirty-three patients were enrolled in this analysis. Median age was 71 years (range: 42–84 years). Median follow-up was 73 months (range: 7–172). Median PSA max at recurrence was 2.9 ng/mL (range: 0.04–21.0 ng/mL). ISUP grade 1 was diagnosed in 15% of patients, 2 – in 17%, 3 – in 10%, ≥ 4 – in 16%, and in 42%, it was not determined. The comparison of groups with different fractionation revealed that patients in the “2x13 Gy” group were significantly older (p=0.04), their PSA level and Gleason score at recurrence were significantly higher (p=0.026 and p=0.044, respectively), the disease was more advanced (p=0.0000) and overall treatment time (OTT) was significantly shorter (p=0.0000).

In the whole group, median BC was 95 months, 2- and 5-year BC was 78% and 61.5%, respectively. Median LC was 104 months. Two- and 5-year LC was 91.5% and 74%, respectively. The median DMFS and DFS was 125 months and 70 months, respectively. Two- and 5-year DMFS was 87% and 72%, respectively; 2- and 5-year DFS was 81% and 56%, respectively. There was statistically significant difference in LC (p=0.012), BC (p=0.037), DMFS (p=0.003) and DFS (p=0.0011) between “3x10 Gy” and “2x13 Gy” groups. (Table 1). No difference in OS was observed between the groups (p=0.38). In the subgroup of patients with local recurrence only (without regional/distant metastases), the difference in DMFS and DFS remained statistically significant (p=0.038 and p=0.009, respectively). The toxicity comparison of these two regimens is still being analysed. The final results will be attached if the abstract is accepted.

Conclusion