ESTRO 2024 - Abstract Book

S2600

Clinical - Urology

ESTRO 2024

Rectal bleeding (RB) is a common adverse event after curative radiotherapy (RT) for prostate cancer (PCa). Due to the expanding use of RT in the treatment of PCa, it is expected that the group of patients experiencing RT related adverse events will also increase. Improved understanding of risk factors for RB is necessary as a guide for future treatment strategies and as a help in the development of preventive strategies.

This prospective study aims to investigate risk factors for RB in patients with PCa receiving RT.

Material/Methods:

In the present prospective registration study, 311 patients with PCa (cT1-cT3N0M0) treated with RT were enrolled from 2017 to 2022. Treatment included RT with VMAT and androgen deprivation therapy (ADT) in selected patients. The RT schedule consisted of 60 Gy/20 fractions (fx) or 78 Gy/39 fx to the prostate alone in patients with low to intermediate-risk disease. Patients with high-risk disease were treated with 56 Gy/39 fx to the elective lymph nodes and seminal vesicles and a boost with 78 Gy/39 fx to the prostate alone (≤T3a) or prostate and seminal vesicles (T3b). Rectal dose objectives were V30Gy≤50%, V57Gy≤15% and V60Gy≤1%, and V50Gy≤50%, V70Gy≤20% and V74Gy≤12% of the rectum volume, respectively for the two dose and fractionations schemes. Systematic collection of staff assessed morbidity was done with the common terminology criteria for adverse events (CTCAE v4.0). Patient-reported outcomes were assessed with the Expanded Prostate Cancer Index Composite (EPIC), EORTC QLQ-C30, and supplementary questions from QLQ-PR25. Morbidity was collected at baseline (BL), at end of treatment (EOT), and at regular intervals during a five-year follow-up (4w, 3m, 6m, 9m, 12m, 18m, 24m, 30m, 36m, 48m, 60m). Patient reported RB was assessed using the EPIC, item 11 “How often have you had bloody stools during the last 4 weeks”. Prevalence rates of RB at BL and each follow-up were calculated. Kaplan-Meier analysis was used to estimate time to event distributions. Risk factors for RB including age, ADT, Body Mass Index (BMI), Charlson Comorbidity Index (CCI), WHO performance status (PS), cancer risk type (high risk vs low-to intermediate risk) as well as patients receiving 78 Gy/39 fx to seminal vesicles (T3b) compared to patients with ≤T3a, smoking at BL and history of hemorrhoids at every follow-up were analyzed using univariate and multivariate Cox regression analyses.

Results: