Prostate Cancer Coverage from Every Angle
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KEYNOTE-365 Update on Pembrolizumab Plus Chemotherapy for Metastatic Prostate Cancer

By: Lauren Harrison, MS
Posted: Wednesday, March 17, 2021

Triplet therapy of pembrolizumab, docetaxel, and prednisone yielded improved objective response and prostate-specific antigen (PSA) response rates after continued follow-up in patients with metastatic castration-resistant prostate cancer. These data represent an additional year of follow-up of the KEYNOTE-365 trial. Leonard Joseph Appleman, MD, PhD, of the University of Pittsburgh Medical Center, presented these study updates on behalf of his colleagues during the virtual 2021 Genitourinary (GU) Cancers Symposium (Abstract 10).

This phase Ib/II trial enrolled patients with metastatic castration-resistant prostate cancer who were either intolerant or nonresponsive to at least 4 weeks of therapy with abiraterone or enzalutamide. The 104 patients in this cohort had disease progression within 6 months of screening (determined by PSA disease progression or radiologic bone/soft-tissue disease progression). Patients received 200 mg of intravenous pembrolizumab every 3 weeks, 75 mg/m2 of intravenous docetaxel every 3 weeks, and 5 mg of oral prednisone twice a day. PD-L1–positive tumors were seen in 23% of this population, 25% had visceral disease, and 50% had measurable disease.

The median time between patient enrollment and data cutoff was 32.4 months. Most patients (101) discontinued therapy, and 77.9% discontinued therapy due to disease progression. The objective response rate was 23.1%, representing the 12 patients who achieved a partial response. The disease control rate (defined as complete response, partial response, noncomplete response, and nonprogressive disease) was 76.0%. The median duration of response was 6.3 months, and the median overall survival was 20.2 months.

Treatment-related adverse events occurred in 100 patients (96.2%). The most frequently seen adverse events were diarrhea (41.3%), fatigue (41.3%), and alopecia (40.4%). Grade 3 to 5 treatment-related adverse events were noted in 44.2% of the study population. There were five deaths associated with treatment-related adverse events, including two from treatment-related pneumonitis.

Disclosure: For a full list of authors’ disclosures, visit coi.asco.org.



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