Patterns of recurrence following radiation and ADT for pathologic lymph node positive prostate cancer: A multi-institutional study

Background and objective: 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: 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.

Key findings and limitations: 270 patients were included, with a median follow-up of 48 months. 256 (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) post-operative PSA. ADT was ST (20%) or LT (68%, median 24 months), while 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-<0.5 ng/mL, 60% for PSA 0.5-2 ng/mL, and 35% for PSA >2 ng/mL (p<0.0001). On multivariable analysis, pre-RT PSA >0.5 (0.5 to 2.0 vs <0.1 HR=2.97; >2.0 vs <0.1 HR=7.63), use of LT ADT vs no ADT (HR=0.43) and use of LT ADT compared to ST ADT (HR= 0.34), Grade group 4 vs 2 (HR=4.11), and positive surgical margins (HR 1.773) were significantly associated with bPFS.

Conclusions: Post-prostatectomy RT at PSA <0.5 ng/mL is associated with favorable bPFS in pN1 prostate cancer.