Clinical outcomes for radiographic node-positive prostate cancer following definitive radiotherapy.

352 Background: The incidence of regional lymph node metastases at diagnosis is approximately 15%. Androgen deprivation therapy (ADT) with radiotherapy (RT) remains a standard treatment option, but long-term effects and outcomes are understudied. Methods: Data was retrospectively collected from 304 subjects with radiographic node-positive prostate cancer treated with RT from 2014-2024. Covariates include use of androgen receptor signaling inhibitors (ARSI), use of brachytherapy boost to primary disease in prostate, pre-RT PSA, and Gleason Score (GS). Endpoints included biochemical progression (bPFS), distant metastases free survival (DMFS) and overall survival (OS). Kaplan-Meier method, log rank test, univariate (UVA) and multivariate regression analyses (MVA) were used for time to event endpoints. Results: Patient features are summarized in table. 48% of patients had ECOG 0. On MVA, GS 9-10 was significantly associated with worse OS (HR 2.26, 95%CI 1.15 – 4.43, p=0.02), DMFS (HR 2.37, 95%CI 1.32 – 4.24, p<0.01) and bPFS (HR 2.10, 95%CI 1.23 – 3.59, p<0.01). Worse performance status was associated with significantly worse OS (HR 3.14, 95%CI 1.35 – 7.29, p<0.01), DMFS (HR 2.03, 95%CI 0.95 – 4.35, p=0.07) and bPFS (HR 2.01, 95%CI 0.99 – 4.07, p=0.05). Radiation boost dose to involved lymph nodes was significantly associated with OS (p=0.03) and DMFS (p=0.03) but not bPFS. There were no other statistically significant associations on MVA. There was no significant association on UVA between pre-radiation maximum PSA and OS, DMFS, or bPFS. Conclusions: In this cohort of patients treated with ADT and definitive RT, 5-year DMFS was 67%. Gleason score and age were the strongest prognostic features. There was no significant association, but there was numerically higher survival seen with use of ARSI or brachytherapy boost. Future work includes characterizing patterns of care and failure to help optimize management. Characteristics and univariable regression results for OS, DMFS, and bPFS using age and pre-RT PSA as continuous variables. N (%) 5yr OS HR (95%CI) p-value 5yr DMFS HR (95%CI) p-value 5yr bPFS HR (95%CI) p-value Age (continuous) Median age (IQR) 69 (64 – 75) 74% 1.04 (1.00 – 1.09) p=0.07 67% 1.02 (0.99 – 1.06) p=0.2 65% 1.02 (0.99 – 1.05) p=0.3 Gleason 8 156 (54%) 83% 74% 71% 9-10 135 (46%) 69% 2.05 (1.06 – 3.95) p=0.03 62% 2.17 (1.25 – 3.77) p<0.01 60% 2.06 (1.22 – 3.49) p<0.01 Brachytherapy Use Yes 86 (28%) 80% 0.60 (0.27 – 1.35) p=0.2 79% 0.62 (0.31 – 1.22) p=0.2 79% 0.61 (0.32 – 1.16) p=0.13 ARSI Use Yes 182 (60%) 78% 0.91 (0.50 – 1.64) p=0.7 67% 0.90 (0.54 – 1.50) p=0.7 67% 0.79 (0.48 – 1.29) p=0.3 Volume Nodal Boost – Below median Median (IQR) 16.1 cc (7.3 – 33.9) 76% 0.99 (0.54 – 1.80) p>0.9 72% 0.93 (0.55 – 1.56) p=0.8 68% 1.05 (0.64 – 1.73) p=0.8 Volume of radiographically involved lymph nodes assessed as binary variable.