ESTRO 2024 - Abstract Book

S2432

Clinical - Urology

ESTRO 2024

A total of 86 pts, with a median age at recurrence of 71 years, were included in the analysis.

The majority (91%) of patients underwent a schedule of 35 Gy in 5 fractions (BED = 198.3 Gy). Median tumor volume (data available for 63 patients) was 81 mm2 (IQR 43 - 149).

Concerning acute toxicities, 15 patients experienced GU Grade (G) 1 toxicities, while only one patient reported acute GU G2 toxicity. Nine patients had acute GI G1 toxicities. No G≥3 GU/GI acute toxicities were reported. After a median follow-up of 17.9 months (range 3.9 – 99.2 months), 29 (34%) patients experienced a BCR with a median time to BCR of 17.9 months (range 5.3 - 69.1 months) and a median PSA at recurrence of 1.66 ng/ml (0.79, 2.83); a total of 27 (26%) of patients had CR with a median time to CR of 23.0 months (range 6.0 – 69.3 months). Four patients were lost at follow-up and were not considered for the Kaplan-Meier analysis. The difference in survival probability stratifying patients according to BED was statistically significant (p = 0.033) in favor of patients who received a BED greater than 198.3 Gy (Figure 1). No statistically significant differences were found stratifying patients according to staging imaging and ISUP. Results of Univariate analysis of CR are shown in Figure 2. At univariate Cox regression analysis (Figure 2), only PSA nadir was significantly associated with CR.

Conclusion:

These preliminary data showed that targeting macroscopic bed recurrence with SBRT resulted to be safe and effective. Additional data and longer follow-up will provide a clearer indication on the right way to treat these patients and on the more appropriate staging methodology for this cohort of patients.

Keywords: SBRT, clinical relapse, prostate