A prospective study of the relationship between clinical outcomes of enzalutamide and serum androgen levels measured by LC-MS/MS in patients with CRPC.

Abstract

146 Background: Enzalutamide (ENZ) is commonly used to treat patients with castration resistant prostate cancer (CRPC). However, the kinetics of serum androgen levels before and after ENZ treatment are unknown. We elucidated the kinetics of serum androgens and explored the possibility of identifying a useful marker for predicting the effects of ENZ. Methods: We conducted a prospective study from 2014 to 2018 at Gunma University Hospital and related facilities. 104 CRPC patients treated with ENZ were analyzed. We investigated the PSA reduction rate (50%, 90%), PSA-progression-free survival (PFS), and overall survival (OS) after administration. To measure levels of androgens accurately we measured serum androgen levels using LC-MS/MS. OS and PSA-PFS were assessed according to the PCWG 2 criteria. This study was approved by the Institutional Review Board of Gunma University Hospital (No. 1177). Results: The 50% and 90% PSA decline rates were 62.5% and 25.0%, respectively. Median serum testosterone (T), dihydrotestosterone (DHT), androstenedione (A-dione), and dehydroepiandrosterone-sulfate levels were 49.0, 5.8, 222.2, and 326.3 pg/ml, respectively. Mean serum levels of T, DHT, and A-dione increased significantly 12 and 24 weeks after compared to before treatment (p < 0.05). We performed a multivariate analysis using a Cox regression to predict OS and PSA-PFS. ECOG PS (0 vs. 1–2), hemoglobin (Hb ≥ 12.5 vs. < 12.5 g/dL), albumin (≥ 3.9 vs. < 3.9 g/dL), visceral metastasis (no vs. yes), EOD (0–2 vs. 3–4), docetaxel treatment (no vs. yes), and DHT level (≥11.25 vs. < 11.25 pg/mL, 11.25 was third quartile) were significant predictors of OS (p < 0.05). Hb (≥12.5 vs. < 12.5 g/dL), docetaxel treatment (no vs. yes), and level of DHT (≥ 5.9 vs. < 5.9 pg/mL) were significant predictors of PSA-PFS (p < 0.05). As a result of the binomial logistic analysis of the predictors of fatigue and decreased appetite, the presence of visceral metastasis (yes) and low DHT (<5.9 pg/mL) were significant predictors of expression. Conclusions: These results suggest that serum androgen levels before ENZ treatment may be useful for predicting efficacy, prognosis, and the incidence of adverse events.