AUA 2019: Rates and Patterns of Metastases in Patients with Node-Negative Prostate Cancer at Radical Prostatectomy Experiencing PSA Failure: Post-Hoc Analysis of RTOG 9601 Trial Data

Chicago, IL (UroToday.com) Until recently there remained a debate as to whether patients undergoing salvage EBRT should definitely be concomitantly treated with androgen suppression. The recently published RTOG 9601 phase III RCT assessed bicalutamide monotherapy among salvage EBRT patients randomized to bicalutamide 150 mg PO daily vs placebo for 24 months [1]. Overall survival rates at 12 years were 76.3% for patients taking bicalutamide compared to 71.3 taking a placebo (p=0.04). Prostate cancer survival rates at 12 years were 5.8% for bicalutamide compared to 13.4% for placebo (p<0.001). At tthe prostate cancer session at AUA 2019, Dr. Sood and colleagues assessed rates and patterns of local and metastatic disease occurrence in patients with node-negative non-metastatic prostate cancer at radical prostatectomy that experience PSA elevation (recurrence or persistence) and undergo salvage radiation therapy.

Data for this post-hoc analysis included demographic, tumor-specific, treatment-specific, and local and metastatic disease occurrence data from 760 men who participated in the RTOG 9601 trial were extracted using the Project Data Sphere platform. Specific covariates included age, race, Karnofsky performance score, pathologic Gleason score, pT stage, surgical margin status, PSA nadir after surgery, pre-salvage radiation therapy PSA and receipt of bicalutamide vs placebo. Patients were stratified into PSA recurrence (post-RP PSA nadir < 0.5 ng/ml) or PSA persistence (post-RP PSA nadir =>0.5 ng/ml) groups, based on cutoffs reported in the original trial. Inverse probability of treatment weighting (IPTW) analysis was utilized to minimize the baseline differences among the groups. Competing risk analysis tested the impact of PSA persistence versus recurrence on local and metastatic disease in the IPTW-adjusted model.

Patients that experienced PSA persistence had higher Gleason grade disease (p=0.027), more advanced pathological stage (p=0.024), and higher PSA levels at the time of receipt of salvage therapy (p < 0.001). All patients received salvage radiation therapy, and approximately 50% of the patients in each group received concomitant anti-androgen therapy (p=0.951). Over a median follow-up of 12 years, in the IPTW-adjusted cohort, the 10-year local recurrence rates were 3.2% versus 1.4% in patients with persistent versus recurrent PSA (Gray test p=0.0001). Similarly, 10-year metastatic recurrence rates were 28.6% versus 10.1% in patients with persistent versus recurrent PSA (Gray test p < 0.0001).

Dr. Sood made several concluding remarks:

This is the first study to compare outcomes among patients with PSA persistence vs recurrence in the contemporary era
Patients with PSA persistence after radical prostatectomy are approximately 2.5 times more likely to experience local and metastatic disease when compared to patients with PSA recurrence after radical prostatectomy, despite local salvage radiation therapy with/without anti-androgen therapy
In the future, it may be worth investigating higher salvage radiation therapy doses or earlier salvage radiation therapy, in general

Presented by: Akshay Sood, MD, Henry Ford Hospital, Detroit, Michigan
Co-authored by: Jacob Keeley, Sohrab Arora, Deepansh Dalela, Wooju Jeong, Craig G Rogers, James Peabody, Mani Menon, Firas Abdollah, Detroit, Michigan

Written by: Zachary Klaassen, MD, MSc, Assistant Professor of Urology, Georgia Cancer Center, Augusta University, Medical College of Georgia, Twitter: @zklaassen_md at the American Urological Association's 2019 Annual Meeting (AUA 2019), May 3 – 6, 2019 in Chicago, Illinois

References:
1. Shipley WU, Seiferheld W, Lukka HR, et al. Radiation with or without Antiandrogen Therapy in Recurrent Prostate Cancer. N Engl J Med 2017;376(5):417-428.

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