Impact of percent positive biopsy cores on cancer-specific mortality for patients with high-risk prostate cancer

Objective: A high percent positive biopsy cores (PBC), typically dichotomized at ≥50% is prognostic of worse cancer-specific outcomes for patients with low- and intermediate-risk prostate cancer (CaP). The clinical significance of ≥50% PBC for patients with high-risk disease is poorly understood. We examined the association between ≥50% PBC, compared to <50% PBC, and prostate cancer-specific mortality (PCSM) for patients with high-risk disease.

Materials and methods: We identified 7,569 men from the Surveillance, Epidemiology, and End Results program who were diagnosed with high-risk CaP (Gleason score of 8-10, prostate-specific antigen >20 ng/mL, or cT3-T4 stage) in 2010-2011 and had 6 to 24 cores sampled at biopsy. Multivariable Fine and Gray competing risks regression was utilized to examine the association between ≥50% PBC and PCSM.

Results: Median follow-up was 3.8 years. 56.2% of patients (4,253) had ≥50% PBC. On competing risks regression, ≥50% PBC was associated with a significantly higher risk of PCSM compared to <50% PBC (adjusted hazard ratio [AHR] 2.00, 95% confidence interval [CI] 1.48-2.70, P < 0.001). On subgroup analyses, ≥50% PBC was associated with a significantly higher risk of PCSM only for cT1-T2 disease (AHR 2.23, 95% CI 1.62-3.07) but not cT3-T4 disease (AHR 0.83, 95% CI 0.39-1.76), with a significant interaction (P_interaction = 0.016). No significant interactions by Gleason score, prostate-specific antigen level, use of definitive therapy, or number of biopsy cores sampled were observed.

Conclusion: In this large cohort of patients with high-risk CaP, ≥50% PBC was independently associated with an approximately 2-fold increased risk of PCSM for patients with cT1-T2, but not cT3-T4, tumors. Percent PBC, which is a widely available clinical value, should be routinely used to risk stratify men with high-risk disease and identify patients whom may benefit from treatment intensification.