ESTRO 2024 - Abstract Book

S2293

Clinical - Urology

ESTRO 2024

126

Digital Poster

The impact of dose-escalated RT on ADT in patients with intermediate risk prostate cancer

Cem Onal 1,2 , Ozan Cem Guler 1 , Gurcan Erbay 3 , Aysenur Elmali 2

1 Baskent University Faculty of Medicine, Department of Radiation Oncology, Adana, Turkey. 2 Baskent University Faculty of Medicine, Department of Radiation Oncology, Ankara, Turkey. 3 Baskent University Faculty of Medicine, Department of Radiology, Adana, Turkey

Purpose/Objective:

Intermediate-risk prostate cancer (IR-PC) patients encompasses a diverse population with varying clinical and pathological characteristics, accounting for the vast majority of patients who receive definitive therapy.Previous studies has shown that combining androgen deprivation therapy (ADT) with radiotherapy (RT) improves biochemical disease free survival (bDFS) and overall survival (OS). However these trials have been criticized for using suboptimal radiation doses of 66 – 70 Gy. The purpose of this study is to identify patients with intermediate-risk prostate cancer (IR-PC) who benefited from 6 months of androgen deprivation therapy (ADT) and/or dose escalated radiation therapy (DE-RT) using the simultaneous-integrated boost (SIB) technique, which delivered 78 Gy to the prostate and 86 Gy to the IPL, in terms of biochemical failure (FFBF) and prostate cancer specific survival (PCSS).

Material/Methods:

A retrospective analysis of 320 IR-PC patients treated between January 2012 and April 2021 was performed. Patients were divided into three groups based on their treatment arm: 78 + ADT (109 patients, 34.1%), 78/86 (102 patients, 31.8%), and 78/86 + ADT. The primary endpoint was FFBF, with PCSS, and acute and late GI and GU toxicities serving as secondary endpoints. Univariable and multivariable analyses were used to determine prognostic factors for FFBF and PCSS.

Results:

The median age of the entire group was 69 years (range, 51 – 85 years), and the median serum PSA level prior to treatment was 11.5 ng/mL (range, 1.0 –19.9 ng/mL). More than 2/3 of patients (67.2%) had clinical ≥T2b disease, and 65 patients (20.3%) had favorable IR (FIR), while 255 patients (79.7%) had unfavorable IR (UIR) disease. The ADT was used in 181 UIR patients (71.0%), which was significantly higher than the FIR group (37 patients, 50.9%; p = 0.02). However, there was no significant difference in DE-RT treatment between the FIR and UIR groups (66.2% vs. 65.9%; p = 0.55).Median follow-up was 8.8 years. Median follow-up time for patients in 78 + ADT group [12.9 years (IQR = 11.9 – 15.4 years)] was significantly longer than 78/86 Gy group [7.1 years (IQR = 5.1 – 8.4 years); p <0.001] and 78/86 + ADT group [7.8 years (IQR = 6.8 – 8.8 years); p <0.001]. The 8-year FFBF and PCSS rates were 88.6% and 99.0%. Disease progression was observed in 45 patients (7.3%), with a median of 41.9 months (13.1 – 107.3 months) after completion of RT. Of these patients, 12 (1.9%) had BF only, 31 (5.3%) had both BF and distant metastasis (DM), and