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

Abstract

78 Background: 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. The prognostic value of ≥50% PBC for patients with high-risk disease is poorly understood. We examined the association between ≥50% PBC and prostate cancer-specific mortality (PCSM) for patients with high-risk prostate cancer. Methods: We identified 7,569 men from the Surveillance, Epidemiology, and End Results program who were diagnosed with high-risk prostate cancer (Gleason 8-10, prostate-specific antigen > 20 ng/mL, or cT3-T4 stage without evidence of nodal or metastatic disease) in 2010 or 2011 and had 6-24 cores sampled at biopsy. Multivariable Fine and Gray competing risks regression was utilized to examine the association between ≥50% PBC and PCSM, with adjustments for sociodemographic and clinicopathologic factors. Results: Median follow-up was 3.8 years (interquartile range 3.3-4.3 years). 56.2% of patients (4,253) had ≥50% PBC. The 4-year unadjusted cumulative incidences of PCSM were 2.0% (95% confidence interval [CI] 1.5-2.6%) and 5.6% (95% CI 4.9-6.4%) for patients with < 50% and ≥50% PBC, respectively. On multivariable analysis, the presence of ≥50% PBC was associated with a significantly higher risk of PCSM (adjusted hazard ratio [AHR] 1.95, 95% CI 1.43-2.66, P< 0.001). On subgroup analysis, ≥50% PBC was associated with a significantly higher risk of PCSM only for cT1-T2 disease (AHR 2.21, 95% CI 1.59-3.07, P< 0.001) but not cT3-T4 disease (AHR 0.77, 95% CI 0.33-1.81, P= 0.547), with a significant interaction ( Pinteraction= 0.012). Conclusions: In this large, contemporary cohort of patients with high-risk prostate cancer, ≥50% PBC was independently associated with a two-fold increased risk of PCSM for patients with cT1-T2, but not cT3-T4, tumors. Percent PBC should be used to routinely risk stratify men with high-risk disease and identify patients who may benefit from intensification of therapy, such as adding docetaxel or abiraterone to radiotherapy with androgen deprivation therapy, to optimize cancer-specific outcomes.