ESTRO 2024 - Abstract Book

S2593

Clinical - Urology

ESTRO 2024

From September 2020 to May 2023 a total of 70 patients were treated, 35 patients for each SBRT schedule, with a median age of 75 (59-85) years. Median follow-up was 14 (6-36) months.

Table 1 displays their baseline demographic and clinical characteristics, along with treatment details.

Median IPSS was 9 (0-27) at baseline and 6 (1-21) at last follow up. Median PSA level before RT was 8,6 (0,8-42) ng/mL. Median CTV and PTV were 51 (23-115) cc and 107 (54-199) cc, respectively. Forty-one (59%) of patients received ADT. One patient suffered from acute grade (G) 3 genitourinary (GU) toxicity; acute G2 GU events were 24%. No ≥G3 acute gastrointestinal (GI) toxicity was observed; acute G2 GI events were 17%. Late G3, G2 and G1 GU toxicity occurred in 3%, 2% and 31% of patients, respectively. No ≥G3 GI late toxicity was registered. Late G2 and G1 GI toxicity was observed in 1% and 3%, respectively.

Univariate analysis did not identify any factor significantly associated with GI acute and late toxicity.

A significant correlation was detected between acute GU toxicity of any grade and CTV volume, age, and fraction dose. Specifically, smaller prostate volume (P = 0.003), with a cutoff of 54 cc, and older age (mean 76 vs 73 years, P = 0.041), were found protective factors. Additionally, 65.7% of patients who received a lower dose per fraction experienced no acute GU toxicity, compared to 34.3% who received a higher dose per fraction (P = 0.023). Univariate analysis demonstrated that patients in the 5-fraction group suffered from fewer events of late GU toxicity (any grade) compared to the 7-fraction group (32.9% vs. 49.0%, P = 0.022). However, a significantly higher incidence of clinically relevant GU side effects (≥G2) were found to be correlated to increased doses per fraction (5 -fraction group) (P = 0.004).

The use of anticoagulants was found to be a risk factor for the occurrence of late GU toxicity (any grade) (P = 0.023). Baseline IPSS score was not associated with both acute and late GU toxicity.

Conclusion: