Conditional biochemical recurrence-free survival after radical prostatectomy in patients with high-risk prostate cancer.

Background: Conditional survival is defined as the likelihood of subsequent survival given the precondition of having already survived a certain length of time. Most analyses of conditional survival in prostate cancer are not clinically applicable because they do not analyze outcomes conditioned on the durability of cure after treatment. We evaluated the conditional probability of biochemical recurrence (BCR)-free survival (C-BCRFS) after radical prostatectomy (RP) for prostate cancer according to the National Comprehensive Cancer Network risk classification and prognostic factors in patients who survived several years without BCR.

Methods: Between January 2009 and December 2018, 877 patients with complete clinicopathologic and follow-up data were included. Using the Kaplan-Meier estimation, the probabilities of C-BCRFS after RP were estimated in patients who did not experience BCR at 0-4 years. C-BCRFS was analyzed according to the National Comprehensive Cancer Network risk classification and compared using the log-rank test. Prognostic factors at each year without BCR were evaluated using multivariable Cox regression analysis.

Results: The median follow-up duration and patient age were 48 months and 67 years, respectively. As the BCR-free interval increased (baseline, 1, 2, 3, and 4 years after RP), the 5-year C-BCRFS rates improved marginally (74.8%, 83.2%, 89.1%, 93.6%, and 98.5%, respectively). However, the 5-year C-BCRFS rates in the high/very high-risk group rose from 54.0% at baseline to 67.6%, 80.3%, 88.6, and 97.8% after 1-4 years free of BCR, respectively. In patients with a BCR-free duration more than 1 year, only seminal vesicle invasion and pathological Gleason score were significant predictive factors of BCR thereafter.

Conclusion: In the high/very high-risk group, the C-BCRFS markedly improved as the interval without BCR increased. In patients who were BCR-free for several years, seminal vesicle invasion and pathological Gleason score were prognostic factors of continued BCRFS. This is useful not only for patient counseling but also to optimize postoperative follow-up strategies.