Keytruda Plus Chemotherapy Is Not Superior to Chemotherapy Alone in Metastatic Prostate Cancer

Treatment with Keytruda (pembrolizumab) plus the chemotherapy docetaxel failed to improve survival outcomes in patients with metastatic castration-resistant prostate cancer, compared with single-agent chemotherapy.

Findings from the phase 3 KEYNOTE-921 trial demonstrated that there was a small trend toward an improvement in both overall survival and radiographic progression-free survival, but the improvements were not considered statistically significant, meaning that researchers could not definitively say that one treatment method was truly better than the other.

The investigators defined overall survival as the time from treatment randomization to death from any cause and identified radiographic progression-free survival as time from randomization to radiographic disease progression or death from any cause.

“Results from this study serve as an important reminder that metastatic prostate cancer remains very difficult to treat, and more research is needed. We will continue to advance our clinical development program to evaluate Keytruda-based combinations and novel candidates for patients with this disease,” Dr. Eliav Barr, senior vice president, head of global clinical development and chief medical officer at Merck Research Laboratories, said in a company-issued press release. “We are grateful to the patients and investigators for their participation in this study.”

KEYNOTE-921 included approximately 1,000 patients with metastatic castration-resistant prostate cancer who had not yet received chemotherapy for their disease but whose disease progressed on or was intolerant to next generation hormonal agents — such as Xtandi (enzalutamide) or Erleada (apalutamide) — were randomly assigned to receive either Keytruda plus docetaxel and the steroid prednisone or placebo plus docetaxel and prednisone.

Aside from investigating Keytruda plus chemotherapy and prednisone’s effect on survival, the study authors also reviewed how well the treatment regimen improved time to initiation of the first subsequent anti-cancer therapy, as well as objective response and duration of response rates. An objective response rate is defined as the percentage of patients whose disease fully or partially responds to treatment. Time to first subsequent anti-cancer therapy was described as the time from treatment randomization to initiation of the first subsequent anti-cancer therapy or death.

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