Impact of the Percentage of Positive Prostate Cores on Prostate Cancer–Specific Mortality for Patients With Low or Favorable Intermediate-Risk Disease

Abstract

Purpose We investigated whether pretreatment factors predicted time to prostate cancer–specific mortality (PCSM) after conventional-dose and conformal radiation therapy (CRT). Patients and Methods Between 1988 and 2002, 421 patients with low (prostate-specific antigen [PSA] level ≤ 10 ng/mL and biopsy Gleason score ≤ 6) or favorable intermediate-risk (PSA > 10 to 15 ng/mL or biopsy Gleason score 3 + 4, but not both factors) disease underwent CRT (median dose, 70.4 Gy). Cox regression multivariable analysis was performed to determine whether the PSA level, Gleason score, T category, or the percentage of positive cores (% PC) predicted time to PCSM after CRT. After a median follow-up of 4.5 years, 117 (28%) patients have died. Results The % PC was the only significant predictor (Cox P ≤ .03). The relative risk of PCSM after CRT for patients with ≥ 50% as compared with less than 50% PC was 10.4 (95% CI, 1.2 to 87; Cox P = .03), 6.1 (95% CI, 1.3 to 28.6; Cox P = .02), and 12.5 (95% CI, 1.5 to 107; Cox P = .02) in men with a PSA ≤ 10 and Gleason score ≤ 6, PSA ≤ 10 and Gleason score ≤ 7, and PSA ≤ 15 and Gleason score ≤ 6, respectively. By 5 years after CRT, 5% to 9% compared with less than 1% (log-rank P ≤ .01) of these patients experienced PCSM if they had ≥ 50% compared with less than 50% PC, respectively. Conclusion CRT dose-escalation techniques, the addition of hormonal therapy, or both should be considered in the management of patients with low or favorable intermediate-risk disease and ≥ 50% PC.