Prostate Cancer Coverage from Every Angle

Immunochemotherapy for Metastatic Castration-Resistant Prostate Cancer: KEYNOTE-365 Cohort B Update

By: Sarah Campen, PharmD
Posted: Friday, December 4, 2020

The combination of pembrolizumab, docetaxel, and prednisone continued to show antitumor activity and a “tolerable” safety profile in patients with abiraterone- or enzalutamide-pretreated metastatic castration-resistant prostate cancer, based on a cohort B update of the KEYNOTE-365 study. Emanuela Romano, MD, PhD, of the Institut Curie, Paris, and colleagues presented the latest findings of the phase I/II trial during the European Society for Medical Oncology (ESMO) Virtual Congress 2020 (Abstract 620P).

Cohort B included 104 patients with metastatic castration-resistant prostate cancer who had received abiraterone or enzalutamide for up to 4 weeks prior to chemotherapy and whose disease progressed within 6 months of screening. Patients received a combination of pembrolizumab at 200 mg intravenously plus docetaxel at 75 mg/m2 intravenously every 3 weeks and prednisone at 5 mg orally twice daily. Half the participants (51%) had measurable disease, and the median time from enrollment to data cutoff was 19.9 months.

The confirmed prostate-specific antigen (PSA) response rate—a decrease of at least 50% from baseline—was 28% in the 103 patients with a baseline PSA assessment. The objective response rate in patients with measurable disease and at least 27 weeks of follow-up (n = 39) was 18%; all were partial responses, and the median duration of response was 6.7 months. The median radiographic progression-free survival and overall survival were 8.3 months and 20.4 months, respectively.

As for safety, grade ≥ 3 treatment-related adverse events were reported in 40% of patients. Two patients died of treatment-related pneumonitis. The KEYNOTE-921 phase III study of this combination is ongoing.

Disclosure: For full disclosure of the study authors, visit

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