Objective: To evaluate the association between the prostate-specific antigen (PSA) nadir level and the time to nadir (TTN) with biochemical recurrence (BCR) risk after radical prostatectomy (RP) in the Shared Equal-Access Research Cancer Hospital (SEARCH) database. Materials and Methods: This is a retrospective analysis of 1939 men from the SEARCH database treated with RP between 1998 and 2015 with available ultrasensitive PSA nadir within 1-6 months after RP. Uni- and multivariable analyses of PSA nadir and TTN with time from nadir to BCR were performed with Cox models (adjusted for demographics, tumor features, and preoperative PSA). Results: Among men with an undetectable PSA nadir, the TTN was unrelated to BCR (1.0-2.9 vs 3-6 months: hazard ratio [HR] 0.86, P = .46). Regardless of TTN, men with detectable nadir had an increased risk of BCR (TTN of 3-6 months: HR 1.81, P = .024; TTN of 1.0-2.99 months: HR 3.75, P <.001 vs undetectable nadir and TTN of 3-6 months). Among men with a detectable PSA at 1-3 months, 53% had a lower PSA level during follow-up 3-6 months after RP, which was undetectable in 32% and lower but still detectable in 21%. Conclusion: In the post-RP setting, men with both a detectable nadir and a shorter TTN had an increased risk of BCR. Intriguingly, about half of the men with a detectable PSA in the first 3 months after RP had a lower PSA level during follow-up between 3 and 6 months after RP. If confirmed in future studies, this has important implications for patients considering adjuvant therapy based on postoperative PSA values in the first 3 months after RP.
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