Patterns of Recurrence Following Radiation and ADT for Pathologic Lymph Node-Positive Prostate Cancer: A Multi-institutional Study.

Purpose: We evaluate prognostic factors and patterns of recurrence in patients who received RT ± androgen deprivation therapy (ADT) for pathologic node-positive (pN1) prostate cancer (PCa) in a multi-institutional cohort.

Methods and materials: Data from patients with pN1 PCa and received RT with short-term (ST, ≤6 mo) or long-term (LT, >6 mo) ADT were obtained from 4 academic institutions. Biochemical progression-free survival (bPFS) and distant metastasis-free survival (DMFS) were evaluated.

Results: Two hundred seventy patients were included, with a median follow-up of 48 months. Two hundred fifty-six (95%) patients had extracapsular extension, 70% had seminal vesicle invasion, 59% had positive surgical margins, 49% had grade group 5, and 64% had a detectable (>0.1 ng/mL) postoperative prostate-specific antigen (PSA). ADT was ST (20%) or LT (68%, median 24 months), whereas 26 (10%) received no ADT. Biochemical failure (bF) was observed in 29%, with 5% having pelvic nodal failure and 11% having distant metastases. The 4-year bPFS was 72% overall, and was 83% for a pre-RT PSA of <0.1 ng/mL, 76% for PSA 0.1 to <0.5 ng/mL, 60% for PSA 0.5 to 2 ng/mL, and 35% for PSA > 2 ng/mL (P < .0001). On multivariable analysis, pre-RT PSA > 0.5 (0.5-2.0 vs <0.1 hazard ratio (HR), 2.97; >2.0 vs <0.1 HR, 7.63), use of LT ADT versus no ADT (HR, 0.43) and use of LT ADT compared to ST ADT (HR, 0.34), Grade group 4 versus 2 (HR, 4.11), and positive surgical margins (HR, 1.773) were significantly associated with bPFS.

Conclusions: Postprostatectomy RT at PSA < 0.5 ng/mL is associated with favorable bPFS in pN1 PCa.