ESTRO 2024 - Abstract Book

S2452

Clinical - Urology

ESTRO 2024

Keywords: kidney, SBRT, metastasis

1740

Digital Poster

Outcomes and late toxicities with ultra-hypofractionated radiation in non-metastatic prostate cancer

Ankita Mallick, Shashank Shenoy, Moses Arunsingh, Indranil Mallick

Tata medical center, Radiation oncology, Kolkata, India

Purpose/Objective:

Ultra-hypofractionated radiation therapy (UHRT) has shown early encouraging results in mainly low-intermediate risk prostate cancer, with relatively limited data on high-risk patients. There are considerable logistic and cost benefits to this approach. We report medium-term outcomes and late toxicities of ultra-hypofractionated radiotherapy delivered once weekly in a tertiary cancer care center and the correlations of dose-volume data to report late toxicities.

Material/Methods:

102 node-negative, non-metastatic, histopathologically proven patients with adenocarcinoma of the prostate treated between 2013 to 2022 were audited. They were treated to a dose of either 35 Gy or 36.25 Gy in five fractions, once a week with volumetric intensity modulated arc radiation therapy or helical tomotherapy and androgen deprivation therapy (ADT) as applicable. Patients with high-risk disease also received elective nodal irradiation to a dose of 25 Gy in five fractions simultaneously. Oncological outcomes were determined, and late toxicities were ascertained. We also calculated dose-volume correlations for grade 2 or higher genitourinary (GU) and gastrointestinal (GI) late toxicities with several dose levels and maximum dose to rectum and bladder, as well as planning target volume (PTV) and overlap volumes. Among these 102 patients, the median pretreatment PSA was 15.2 ng/ml. Nineteen (18.6%) had Gleason 8 or higher tumors and 43(42.1%) had T3-4 disease. High-risk disease was present in 56 patients (54.9%). Elective nodal radiation was used in 54 (52.9%). The median follow-up was 45 months. The 4-year probability of biochemical control was 86.6% for the whole group (94.8% for low-intermediate risk and 80.7% for high-risk). Distant metastases occurred in 5(8.9%) patients in the high-risk group vs none in the low-intermediate risk group. The 5 year probability of metastases-free survival was 93.6%. Twelve (11.7%) and fourteen (13.7%) patients reported grade 2 late urinary and rectal toxicity respectively. There was no statistically significant difference in PTV and its overlap volumes with rectum and bladder in those who had Grade 0-1 vs Grade 2+ toxicities. There were no dose volume correlation at V5, V10, V15, V20, V25, V30, V35, V36, V36.5Gy for grade 2+ urinary toxicity. For grade 2+ rectal toxicity there was dose volume correlation for V36 (mean 3.2 vs. 1.9Gy p = 0.02), V36.5 (mean 2.0 vs. 0.76 Gy p = 0.02), and maximum dose (37.4 vs. 36.8Gy, p = 0.01). Results: