3222 - Toxicity Outcomes and Patterns of Failure after Whole vs. Partial Gland HDR Brachytherapy as Salvage Treatment for Recurrent Prostate Cancer
Presenter(s)
P. Armstrong1, N. Kiguru2, A. A. Olabumuyi1, J. K. Molitoris1, N. Lamichhane3, J. Xu1, M. Guerrero4, J. Cammin4, S. Mossahebi1, Z. H. Rana1, M. Kim1, S. Kudryasheva5, and M. Naslund6; 1Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, MD, 2University of Maryland School of Medicine, Baltimore, MD, United States, 3University of Maryland Medical System, Baltimore, MD, 4University of Maryland School of Medicine, Baltimore, MD, 5Department of Radiation Oncology, University of Maryland Medical Center, Baltimore, MD, 6Division of Urology, University of Maryland Medical Center, Baltimore, MD
Purpose/Objective(s): High-Dose Rate (HDR) brachytherapy (BT) is an effective salvage treatment for radiorecurrent prostate cancer; however, whole gland treatment has been associated with significant gastrointestinal (GI) and genitourinary (GU) toxicities. Advances in ultrasound-guided brachytherapy, multiparametric MRI, and PSMA-PET now enable precise lesion targeting, making partial gland HDR-BT a compelling salvage treatment alternative. While data suggests partial gland salvage HDR-BT may achieve adequate disease control with lower toxicity, direct comparisons of dosimetric analysis of intraprostatic recurrence patterns, and toxicity profiles between whole and partial gland approaches remain limited. This study hypothesizes that partial gland re-treatment achieves comparable biochemical control to whole gland re-treatment with reduced toxicity.
Materials/Methods: 47 patients treated between 2020 and 2025 for locally recurrent prostate cancer after initial radiation therapy were identified in this single-institution retrospective study. Patient and clinical characteristics, outcomes, and toxicity data were collected via medical record review. Patients received ultrasound-guided HDR-BT with 20 Gy in 2 fractions to either partial or whole gland with a boost to gross disease of 27 Gy. Acute and late GU and GI toxicities were graded per CTCAEv5. For intraprostatic recurrences, HDR dosimetry was reviewed to characterize failure patterns relative to IDL regions. Fisher’s exact test and Kaplan-Meier survival analysis were performed using IBM SPSS v31.
Results: 27 patients (57.4%) received partial gland and 20 (42.6%) received whole gland treatment with a median follow up of 26 months (range: 1 – 61 months). 24-month biochemical control was 81.4% (95% CI: 74.9–87.9) and did not differ between whole and partial gland cohorts (83.2% vs 79.7%; p=0.29). The combined Grade 3+ toxicity rate was 10.6%, with a lower rate in the partial gland cohort (3.7%) versus whole gland (20.0%), though this did not reach statistical significance (p=0.148). 6 of the partial gland patients (22.2%) and 7 of the whole gland patients (35.0%) had a recurrence (p=0.737). 8 of the recurrences were strictly intraprostatic, with 6 in the partial gland HDR-BT cohort. 2 patients had recurrence in the high-dose region (>100% IDL), 1 patient had recurrence in the moderate dose region (50-100% IDL) and 3 patients had recurrence in the low-dose region (<50% IDL).
Conclusion: Partial gland salvage HDR-BT was associated with a lower rate of Grade 3+ toxicities compared to whole gland treatment and with comparable recurrence rates. 33% of intraprostatic recurrences in the partial gland cohort occurred in the highest dose region. These findings support continued investigation of partial gland HDR-BT as a toxicity-sparing salvage strategy