ESTRO 2022 - Abstract Book

S1191

Abstract book

ESTRO 2022

1 Universidad de Valparaiso, Oncology, Valparaiso, Chile; 2 Hospital Carlos Van Buren, Oncology department, Valparaiso, Chile; 3 Hospital Clínico Regional de Valdivia, Oncology, Valdivia, Chile; 4 Universidad Diego Portales, Oncology, Santiago, Chile Purpose or Objective Radiotherapy is a therapeutic option in localized prostate cancer and ultra-hypofractionated regimes (SBRT) are a validated alternative in terms of effectiveness and safety. The purpose of this study is to describe the treatment characteristic and acute toxicity in a multicentric prostate cancer patient cohort treated with SBRT Materials and Methods We performed a retrospective analysis of patients treated with SBRT with a curative intention between 2020-2021 at Carlos Van Buren Hospital - Valparaiso and Valdivia Regional Hospital with a flattening filter free volumetric modulated arc therapy. Online correction was performed before each session. Acute toxicity was defined according to RTOG criteria. In both centers, CTV was defined as: 1) Prostate (low risk patients) 2) Prostate + 1 cm Seminal Vesicles (S.V) (intermediate risk) 3) Prostate + 2 cm S.V (high risk) PTV = CTV +0.5 cm (0.3 cm posteriorly). At Van Buren Hospital Prescription consisted of 36.25 Gy in 5 fractions (alternate days) to Prostate PTV and 27.25 Gy in 5 fractions to S.V PTV. Valdivia’s prescription consisted of 36.25 Gy in 5 fractions uniformly to PTV escalating up to 40 Gy with a simultaneous integrated boost technique to prostate in intermediate and high-risk patients. This study was approved by the local ethics committee. Results 146 patients were included. 55 (37.16%) patients had high risk disease. 118 (79.7%) patients had staging procedures. In 87 (58.8%) patients planning was based on MRI / CT fusion. Gold seeds (fiducial markers) were used In 12 patients. Median PSA was 9.66 (IQR 6.26-17.8). 99 (66.9%) of patients had some sort of acute toxicity. 2 patients suffered from acute G3 gastrointestinal toxicity and 2 patients from acute G3 genitourinary toxicity. No G4-G5 events were observed. One patient had to suspend treatment due to urinary obstruction caused by disease progression.