3260 - Comparison of Survival and Adverse Events in Localized High-Risk Prostate Cancer Treated with IMRT+ADT vs. Trimodality Therapy (LDR-Brachytherapy + EBRT+ADT)

Purpose/Objective(s): To evaluate and compare the survivals and radiotherapy-induced adverse events (AEs) of intensity-modulated radiotherapy (IMRT) with androgen deprivation therapy (ADT) and trimodality therapy, including low-dose iodine-125 brachytherapy, external beam radiotherapy, and ADT, for high-risk localized prostate cancer (LPC).

Materials/Methods: High risk PC patients with T stage = 3a, Gleason score = 8, and initial prostate specific antigen (PSA) = 20.0 ng / dl treated between 2010 and 2021 were retrospectively evaluated. All patients were treated with IMRT plus ADT or trimodality therapy. As for the IMRT group, 78 Gy in 39 fractions or 70 Gy in 28 fractions were delivered. As for the trimodality group, 110 Gy of 125- I seed implantation and basically 45 Gy in 25 fractions of 3-dimensional conformal radiotherapy were delivered. In both groups, ADT was started 6 months before and continued for 2 years after radiation therapy. Survivals, acute and late AEs were evaluated and compared.

Results: A total of 329 patients were evaluated in this study. Two hundred and thirty-eight patients were treated with IMRT, and 91 underwent trimodality. 5- and 7-year biochemical-clinical failure-free survival (BCFFS) rates in the IMRT/trimodality group were 94.9/96.2, and 91.8/91.5%, respectively (P = 0.511). Stratified by 1–2/3 factors, 5- and 7-year BCFFS rates in the IMRT groups were 95.8/91.8, and 95.8/75.6%, respectively (P = 0.009). 5- and 7-year BCFFS rates in the trimodality group were 96.8/94.1, and 91.4/94.1%, respectively (P = 0.995). The cumulative 3-/5-year incidence of late genitourinary AEs in the IMRT/trimodality group was 7.3/8.4, and 15.5/16.9%, respectively (P = 0.037), and the cumulative 3-/5-year incidence of late gastrointestinal AEs was 2.2/3.4, and 11.0/12.2%, respectively (P = 0.001). Thirty patients (9.1%) could not complete long-term ADT.

Conclusion: Treatment results of both IMRT and trimodality were considered to be good, and our results also indicated that the long-term survival of unfavorable high-risk patients with LPC who had three risk factors was poor in the IMRT group. Further treatment experience of both modalities must be accumulated with more appropriate patient allocations.