Enzalutamide Maintenance Following Docetaxel in Metastatic Castration-Naive Prostate Cancer: A Pilot Feasibility Study

Purpose: To assess the feasibility and short-term efficacy of maintenance enzalutamide following first-line docetaxel plus androgen deprivation therapy (ADT) in patients with high-volume, metastatic castration-naive prostate cancer (mCNPC).Materials and Methods: The present study included 38 consecutive patients with mCNPC who did not have disease progression with ADT plus docetaxel between October 2022 and October 2023. Patients received a switch maintenance therapy with enzalutamide until progression, unacceptable toxicity, or patient withdrawal. Endpoints included time to prostate-specific antigen (PSA) progression and safety.Results: Among the 38 patients, the median age was 68 years, and the most frequently observed metastatic site was bone (n=36), followed by lymph nodes (n=28), lung (n=8), and liver (n=1). The median duration of firstline docetaxel was 2.8 months (range, 2.7–5.0 months). At the time of commencing maintenance enzalutamide, the median PSA was 3.2 ng/mL (range, 0.01–258 ng/mL). Maintenance enzalutamide was generally welltolerated. A total of 11 patients (28%) discontinued enzalutamide, and the main reasons included adverse events (prolonged fatigue of grade 1 or 2, n=6), disease progression (n=3) and financial burdens (n=2). Median time to PSA progression was not reached, and 93% were PSA progression-free at 12 months.Conclusions: Maintenance enzalutamide is a feasible treatment option with potential clinical benefit for patients with high-volume mCNPC who were progression-free after first-line ADT+docetaxel.