Blood platelet volume to predict treatment-specific outcomes of metastatic castration-resistant prostate cancer.

Abstract

242 Background: In the present guidelines for the management of metastatic castration-resistant prostate cancer (CRPC), it is unclear who benefits from androgen receptor axis-targeted agents (ARATs) or docetaxel as a first-line treatment. Methods: We conducted a single-institutional retrospective study to explore treatment-specific biomarkers for treatment response of metastatic CRPC. A cohort of 211 patients with metastatic CRPC treated with either ARAT (abiraterone acetate or enzalutamide) or docetaxel as a first-line treatment was evaluated. In addition to well-established biomarkers such as hemoglobin, neutrophil-to-lymphocyte ratio, alkaline phosphatase, and lactate dehydrogenase, we also assessed red cell distribution width, platelet count, and mean platelet volume (MPV). Laboratory measures were assessed within 1 month before starting treatment. Prostate-specific antigen progression-free survival (PSA-PFS) and radiographic progression-free survival (RPFS) were evaluated. Multivariable Cox regression models were used to assess the association between biomarkers and the risk of events. We also studied the statistical interaction between biomarkers and clinical outcomes. Results: Of all blood-based biomarkers, multivariable Cox regression models identified pre-treatment MPV (≤9.0 fL) as an independent prognostic factor of both PSA progression (hazard ratio [HR]: 2.62, 95% confidence interval [CI]: 1.25-5.48, P = 0.011) and radiographic progression (HR: 4.46, 95% CI: 1.79-11.1, P = 0.001). In addition, these models showed a lower risk of PSA progression (HR: 0.38, 95% CI: 0.15-0.96, P = 0.041) and radiographic progression (HR: 0.16, 95% CI: 0.05-0.50, P = 0.002) with docetaxel compared with ARAT when pre-treatment MPV was small. Conclusions: The present study identified MPV as a significant treatment-specific prognostic factor of PSA progression and radiographic progression in patients with metastatic CRPC treated with a first-line treatment. Furthermore, our results suggested that small MPV was associated with superior survival benefit on docetaxel over ARAT.