Retrospective analysis of fatigue in men with metastatic castration-resistant prostate cancer treated with enzalutamide.
374 Background: Enzalutamide (E) improves survival in men with metastatic castration-resistant prostate cancer (mCRPC). Fatigue (F) while taking E is poorly understood and may limit the use of this life-prolonging drug. Methods: All men treated with E for mCRPC at Princess Margaret Cancer Centre from August 2010 and July 2016 were included. Relevant factors collected, include age, ECOG, Charleston Comorbidity Index, disease characteristics, prior therapies, concomitant medications, and details regarding E treatment and response. Univariate (UVA) and multivariate (MVA) analysis were performed using logistic regression. Results: 415 men started E for mCRPC during this period. Median age at diagnosis was 66 years (range 42-94) and median time to castration-resistance (TTCR) was 113 days. Prior therapies included docetaxel (21%) and abiraterone (26%). Bone was the most common site of metastasis (76%) followed by lymph nodes (45%) and visceral (20%). Concurrent corticosteroid use was 18% and PSA response (≥50%) rate was 55%. Median duration on E was 224 days. F on E occurred in 178 patients (43%) and 56 (13%) men required a dose-reduction due to F. 26 men (6%) stopped E due to F (Table). Conclusions: F is an important and common side effect of E in men with mCRPC. Duration of exposure to androgen deprivation, markers of systemic inflammation (such as increased NLR and platelets) and advanced age appear to be associated with E-related F and difficulty administering drug. There was no association between corticosteroid use and E-related F and difficulty administering drug. [Table: see text]