Prognostic Significance of Neuroendocrine Differentiation in Patients With Gleason Score 8–10 Prostate Cancer Treated With Primary Radiotherapy

Abstract

To determine the prognostic significance of neuroendocrine differentiation (NED) in Gleason score 8-10 prostate cancer treated with primary radiotherapy (RT). Chromogranin A (CgA) staining was performed and overseen by a single pathologist on core biopsies from 176 patients from the William Beaumont prostate cancer database. A total of 143 had evaluable biopsy material. Staining was quantified as 0%, <1%, 1-10%, or >10% of tumor cells. Patients received external beam RT alone or together with high-dose-rate brachytherapy. Cox regression and Kaplan-Meier estimates determined if the presence/frequency of neuroendocrine cells correlated with clinical endpoints. Median follow-up was 5.5 years. Forty patients (28%) had at least focal positive CgA staining (<1% n = 21, 1-10% n = 11, >10% n = 8). No significant differences existed between patients with or without staining in terms of age, pretreatment prostate-specific antigen, tumor stage, hormone therapy administration, % biopsy core involvement, mean Gleason score, or RT dose/modality. CgA staining concentration independently predicted for biochemical and clinical failure, distant metastases (DM), and cause-specific survival (CSS). For patients with <1% vs. >1% staining, 10-year DM rates were 13.4% vs. 55.3%, respectively (p = 0.001), and CSS was 91.7% vs. 58.9% (p < 0.001). As a continuous variable, increasing CgA staining concentration predicted for inferior rates of DM, CSS, biochemical control, and any clinical failure. No differences in outcomes were appreciated for patients with 0% vs. <1% NED. For Gleason score 8-10 prostate cancer, >1% NED is associated with inferior clinical outcomes for patients treated with radiotherapy. This relates most directly to an increase in distant disease failure.