ESTRO 2022 - Abstract Book

S183

Abstract book

ESTRO 2022

Results At a median follow-up of 38 months (mean 46±36), 23% of patients died of systemic disease progression. Treatment was well-tolerated by all patients. Acute and late RTOG Gastrointestinal (GI) score of grade 3 occurred in 14% and 0% of the cases (no grade 4), and genitourinary (GU) grade 2 in 5% and 4% (no grade3), respectively. Mean CTV was 418±199cc and 57±46cc for the pelvis and the boost, respectively. Dose coverage was 98±3% (PTV pelv ) and 98±6% (PTV boost ). SB and B sparing was the main reason for reduced PTV coverage. Dose tolerances were met for all OAR with a few exceptions for the B, S and SB (see fig 2), in order to preserve the PTV pelv standard coverage level (25Gy). Dose to FH was exceeded for one patient due to encompassed bone metastasis within the treatment field . QA results were fulfilled for all patients (99±1%), showing that tighter gamma passing rate criteria can be applied.

Conclusion Dose intensification in short-course RT for rectal cancer is a new, feasible and safe approach to be considered in selected rectal cancer patients. Whether SIB-SCRT can achieve higher rates of clinical or pathological responses compared to the standard long-course chemoradiotherapy needs to be evaluated prospectively in randomized clinical trials.