Results of a Real-world Study of Enzalutamide and Abiraterone Acetate With Prednisone Tolerability (REAAcT)

Abstract

Background: The objective of this study was to evaluate differences in tolerability in patients with metastatic castration-resistant prostate cancer treated with enzalutamide (ENZA) or abiraterone acetate plus prednisone (AA+P).

Patients and methods: This was a phase IV, prospective, open-label, multicenter, real-world study. Patients were prescribed ENZA or AA+P at the treating physician's discretion. Computerized tests of 4 cognitive domains (Cogstate), patient-reported outcomes (European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire-Core 30 [EORTC QLQ-30], Functional Assessment of Chronic Illness Therapy-Fatigue [FACIT-Fatigue], Functional Assessment of Cancer Therapy-Cognitive Function [FACT-Cog]), and patient/caregiver surveys were assessed at baseline and 2 months. Safety data were collected.

Results: Of 100 treated patients, 92 were evaluable (46/arm). Baseline characteristics were similar, with mild cognitive impairment observed in ∼20% of patients. The FACIT-Fatigue demonstrated a statistically significant worsening from baseline of -4.00 (95% confidence interval, -6.61 to -1.39) for ENZA compared with AA+P, -0.01 (95% confidence interval, -2.40 to 2.38). Overall, more adverse events (AEs) and more AEs of fatigue were reported with ENZA versus AA+P (52% vs. 36% and 26% vs. 8%, respectively). Grade 3/4 AEs were similar (4% vs. 6%). Unique neuropsychiatric AEs reported with ENZA included amnesia, cognitive disorders, memory impairment, and confusional state; those for AA+P included cerebrovascular accident, presyncope, and spinal cord compression. Clinically meaningful cognitive decline was seen in 4 patients on ENZA versus 1 patient on AA+P. However, the overall mean changes from baseline for the Cogstate tests, the EORTC QLQ-C30, and the FACT-Cog assessment were similar and showed no meaningful change. Caregiver survey responses noted more fatigue with ENZA and more moodiness with AA+P compared with patient responses.

Conclusions: Although baseline values were similar, more fatigue and neurocognitive differences were observed with ENZA compared with AA+P.

Keywords: Clinical trial; Phase IV; Prospective; Prostatic neoplasms; mCRPC.