ESTRO 2024 - Abstract Book

S2415

Clinical - Urology

ESTRO 2024

64 patients completed SABR to PCa metastases. 6 were excluded due to long term ADT. 58 patients were analyzed. Median age was 65 years, median follow up was 37 months (range 2-99 months). Median ADTFS for all patients was 19 months (95% CI 10.8-27.2), rPFS was 20 months (15.4-24.6). 52 (89.7%) patients had a single metastasis treated. 47 patients (81%) were treated with 30Gy in 3 fractions, 8 (13.8%) with 27Gy in 3 fractions and 3(5.2%) with 30Gy in 5 fractions. 12 patients (20.7%) had limited-term ADT alongside SABR, 5 (8.6%) for 6 months, 7 (12.1%) for 2 years. There was no statistically significant difference between rPFS or ADTFS based on Gleason score at diagnosis (≥8 vs <8) (p= 0.598 and p=0.475 respectively), PSA doubling time (>6 months vs<6months), (p=0.672 and p=0.386), initial treatment modality (prostatectomy vs radiotherapy with ADT) (p= 0.821 and p= 0.272), type of metastases treated (bone or nodal) (p= 0.510 and p= 0.513). Of the 40 patients who progressed radiologically, 15 (37.5%) progressed at the site of SABR whereas 25 (62.5%) progressed outside the treated site. The majority of patients started ADT due to radiological progression although 5 (8.6%) started ADT due to biochemical progression alone.

Table 1: Breakdown of median survival figures and p values generated via log-rank test to determine difference between groups

Conclusion:

This retrospective study demonstrates that ADTFS in a real world patient group receiving SABR for oligometastatic PCa was similar that seen in the STOMP trial 1 (19 and 21 months, respectively). RPFS was similar to ADTFS, which was expected, although ADTFS being slightly shorter could be explained by 5 patients starting ADT based on biochemical progression. There is an indication SABR confers good local control at the treated site, with the majority of patients progressing due to metastases elsewhere rather than at the treated site. Greater patient numbers and