ESMO 2020: Adding Pembrolizumab After Enzalutamide Failure in Prostate Cancer
Posted: Thursday, October 1, 2020
The addition of pembrolizumab after the development of resistance to enzalutamide therapy showed antitumor activity in measurable and bone-predominant metastatic castration-resistant prostate cancer. This finding, which represents cohorts 4 and 5 of the multicohort phase II KEYNOTE-199 study, was presented at the European Society for Medical Oncology (ESMO) Virtual Congress 2020 by Aurelius G. Omlin, MD, of Kantonsspital St. Gallen, Switzerland and colleagues (Abstract 623P).
Patients with measurable (cohort 4, n = 81) or bone-predominant nonmeasurable (cohort 5, n = 45) metastatic prostate cancer were included in this trial. Eligible patients had developed resistance to enzalutamide after having an original response to the medication. Enzalutamide was continued, but patients also received 200 mg of intravenous pembrolizumab every 3 weeks until disease progression, toxicity, or withdrawal.
The median time to data cutoff was 15 months in cohort 4 and 19 months in cohort 5. The objective response rate in cohort 4 was 12%, with two patients achieving a complete response and eight achieving a partial response; four of these patients had a response lasting for 6 months or longer, and the median duration of response was 6.3 months. The objective response rate in cohort 5 was not reported. The median progression-free survival was 4.2 months in both cohorts, and the overall survival rate at 12 months was 70% in cohort 4 and 75% in cohort 5.
Grade 3 or higher treatment-related adverse events were present in 26% of patients in cohort 4 and 24% in cohort 5. Immune-related adverse events led to the death of two patients in cohort 4 (Miller Fisher syndrome and myasthenia gravis). Patients experienced a higher incidence of rash of any grade than was previously reported for pembrolizumab or enzalutamide alone, but the rash was manageable with standard-of-care treatments.
Disclosure: For a full list of author disclosures, visit oncologypro.esmo.org.