ESTRO 2024 - Abstract Book

S2476

Clinical - Urology

ESTRO 2024

84 pts were treated between May 2020 and June 2021. Two-years follow-up data are hereby analized. Most pts were UIR (43%), followed by HR (31%), favourable-intermediate risk (FIR, 21%), and low-risk (LR, 5%). The OTT was ≤ 17 days for 57 pts and > 17 days for 27 pts. 59 pts received HT: short-term (6-months) Bicalutamide 150 mg was prescribed to 31 UIR pts, the remaining received long-term LHRH-analogues (HR pts). The 39% of the population had alpha-blocker therapy ongoing at baseline. Previous TURP was reported in 26% of cases (22 pts, of whom 6 pts within 2-years prior to the RT start). Bladder V37 Gy was > 10 cc in 76 pts (91%), in particular ≥20cc in 7/76 pts. According to baseline IPSS evaluation, the 20% of the population had moderate to severe symptoms (score > 12). A prostate volume > 80cc was reported for 9 pts (11%). GU G2+ acute toxicity (up to 3 months from the RT start) events were previously observed in 17 pts (20%). Overall, the incidence of late (6- to 24-months) GU G2+ events was 7.1% (6 pts). Just two pts experiencing acute GU G2+ toxicity developed late G2+ events. In particular, the incidence of GU G2+ toxicity at 6-, 12-, 18- and 24-months was as follows: 1 (1.2%), 4 (4.8%), 2 (2.4%), and 2 (2.4%), respectively. The majority of these events was G2, with the exception for only 1 case of G3 and 1 case of G4 (both at the 12 months timepoint). The following risk factors for late GU G2+ toxicity were identified: bladder V37 Gy > 20cc (p=0.04) and history of TURP (p=0.01; if within 2-years prior to RT start, p<0.001). GI G2 acute toxicity (up to 3 months from the RT start) events were previously observed in 2 pts (2.4%). Overall, the incidence of late (6- to 24-months) GI G2+ events was 6% (5 pts). None of the pts experiencing acute GI G2+ toxicity developed late G2+ events. In particular, the incidence of GI G2+ toxicity at 6-, 12-, 18- and 24-months was as follows: 0 (0%), 2 (2.4%), 4 (4.8%), and 2 (2.4%), respectively. Late GI G3 toxicity was reported in 3 pts (1 at the 12-months timepoint, and 2 at the 18-months timepoint). No late GI G4 toxicity was reported.

Conclusion:

LINAC-based image-guided ultra-hypofractionation appears to be safe in terms of late GU and GI tolerance. Pts at higher risk of developing late GU G2+ toxicity are those more symptomatic at baseline, those with enlarged prostates, TURP history, larger bladder dose-bath, and UIR/HR groups. Longer-lasting RT treatments and the use of HT appeared to be protective in terms of late GU events incidence. Our analysis further supports the HYPO-RT-PC [1] and PACE-B [2] data.

Keywords: Prostate, Ultra-hypofractionation, Toxicity

References:

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