(P005) Ultrasensitive PSA Identifies Patients With Organ-Confined Prostate Cancer Requiring Postop Radiotherapy

Jung Julie Kang, MD, PhD, Robert Reiter, MD, Patrick Kupelian, MD, Michael Steinberg, MD, Christopher R. King, PhD, MD; Department of Radiation Oncology, Department of Urology, UCLA

PURPOSE/OBJECTIVES: Randomized controlled trials have shown that adjuvant radiotherapy (RT) after radical prostatectomy (RP) improves biochemical relapse-free and overall survival in patients with extracapsular disease. However, even patients with organ-confined disease are at risk for failure. This study analyzes postoperative (postop) ultrasensitive prostate-specific antigen (uPSA) in the surveillance of these patients.

MATERIALS AND METHODS: From 1991–2013, 146 patients with pT2N0 disease who were referred for a rise in PSA after RP were identified: 85 were margin-positive (m+), and 61 were margin-negative (m−). Surgical approach (open vs robotic), initial PSA (iPSA), Gleason grade, margin status, and postop uPSA were covariates for analysis. Median first postop PSA and follow-up were 3 and 38 months, respectively. The uPSA threshold was 0.01 ng/mL.

Benign uPSA patterns occurred from 0.01–0.02 ng/mL; thus, ≥ 0.03 ng/mL was defined as uPSA failure. True (conventional) biochemical relapse (tBCR) was defined as PSA ≥ 0.2 ng/mL. Patients were censored at last follow-up or adjuvant therapy. Kaplan-Meier and Cox multivariate analyses were used to compare tBCR rates.

RESULTS: Median time to tBCR for the entire cohort was 50 months. The m+ patients revealed a more indolent course than m− patients (median time to relapse: 86 mo for m+ vs 33 mo for m−; P = .0003). No differences in Gleason grade or iPSA between m+ and m− patients were seen.

On multivariate analysis (MVA), only first postop uPSA ≥ 0.03 ng/mL (hazard ratio [HR] = 4.1; P < .001) and margin status (m−: HR = 5.6; P = .0315) independently predicted for time to tBCR.

First postop uPSA ≥ 0.03 ng/mL discerned tBCR with much greater sensitivity than undetectable first conventional PSA < 0.2 ng/mL (44% vs 19%). First postop uPSA < 0.03 ng/mL vs. ≥ 0.03 ng/mL predicted median tBCR at 61 vs 10 months (P = .0003). Any postop uPSA ≥ 0.03 ng/mL captured all failures missed by analyzing only the first postop value (100% sensitivity).

Using uPSA ≥ 0.03 ng/mL to identify relapse yields a substantial (33 mo) lead time advantage over waiting until conventional relapse at PSA ≥ 0.2 ng/mL (median 17 vs 50 mo in favor of uPSA ≥ 0.03 ng/mL).

CONCLUSIONS: Only first postop uPSA ≥ 0.03 ng/mL and margin status independently predicted biochemical relapse for organ-confined prostate cancer. The m− patients exhibited much earlier failures, suggesting greater biologic aggressiveness.

Biochemical failure can be called at uPSA ≥ 0.03 ng/mL with excellent sensitivity, and adopting it offers an impressive lead time advantage over the conventional failure definition (PSA ≥ 0.2 ng/mL).

Integrating uPSA into the immediate and continued frequent surveillance of RP patients with organ-confined cancer will improve postop RT outcomes by identifying failures sooner and promoting an early salvage strategy.

Proceedings of the 97th Annual Meeting of the American Radium Society - americanradiumsociety.org