Five-year outcomes of SABR in intermediate- and high-risk prostate cancer without ADT.

5101 Background: Stereotactic ablative body radiotherapy (SABR) is emerging as a prominent treatment option for localized prostate cancer (PCa). Most existing studies have primarily focused on low- and intermediate-risk PCa patients, who typically have favorable prognoses regardless of treatment. Additionally, the necessity of adding androgen deprivation therapy (ADT) remains a subject of ongoing debate, given its associated side effects and limited impact on overall survival (OS). In this study, we present the long-term outcomes of patients predominantly with intermediate- and high-risk PCa who were treated with SABR without ADT. Methods: This was a single-center prospective study of 87 patients with localized PCa who underwent SABR without subsequent ADT. SABR was delivered in an ultra-hypofractionation regimen (36.0 – 42.7 Gy) using Varian TrueBeam/EDGE linear accelerators between July 2015 and June 2024. The primary endpoint was biochemical recurrence-free survival (bRFS), with secondary endpoints including toxicity and overall survival (OS). Results: A total of 87 patients, with a median age of 68.8 years (range: 50–86 years), were included. The median follow-up period was 31 months (range: 3–105 months). The distribution of patients by risk group was as follows: low-risk (21.8%), intermediate-risk (55.1%), and high-risk (17.9%). The 1-, 3-, and 5-year bRFS rates were 97.6%, 92.2%, and 90.0%, respectively. Importantly, no patient died as a result of PCa progression during the observation period. No clinically significant toxicity was reported. Conclusions: The findings of this study suggest that SABR as a standalone treatment modality is a safe and effective approach for localized PCa, providing durable biochemical control without significant toxicity. However, further investigations involving larger patient cohorts and longer follow-up periods are needed to confirm these results and enhance their reliability.