Trial Shows Keytruda With Chemotherapy Superior to Chemo Alone

Results of a new phase 3 clinical trial published in the Journal of Clinical Oncology indicate that a chemoimmunotherapy regimen combining chemotherapy with immunotherapy drugs improves patient survival more than chemotherapy alone for pleural mesothelioma.

Study researchers used pembrolizumab (Keytruda) alongside platinum and pemetrexed chemotherapy. Christina S. Baik, MD, MPH, reviewed the phase 3 trial results during the American Society of Clinical Oncology’s 2023 Best of ASCO Seattle annual meeting. 

The overall response rate for patients receiving Keytruda with chemotherapy was 63% compared to 40% for those on chemotherapy alone. 

“This was a fairly simple study design,” Baik said. “Patients who received chemoimmunotherapy did better. They had improved overall survival compared with chemotherapy alone, with a hazard ratio of around 0.8.” 

Keytruda targets the PD-1 receptor on lymphocytes, a type of white blood cell, and allows the immune system to target mesothelioma tumors better. Results from the clinical trial showed that patients with both PD-L1-positive and PD-L1-negative tumors experienced survival improvements.  

Keytruda With Chemotherapy Improves Survival Rates

Pharmaceutical company Merck first announced preliminary results in June. The multimodal treatment of Keytruda and chemotherapy led to a 21% reduction in the patient’s risk of death. 

The study enrolled 440 patients with pleural mesothelioma who had not received previous treatment. Patients in the chemoimmunotherapy arm showed a median overall survival of 17.3 months versus 16.1 months for those on chemotherapy alone. 

Patients with nonepithelioid mesothelioma cell types benefitted more significantly than those with epithelioid tumors. About 20% of participants had grade 3 or higher adverse effects, the most common being fatigue. The report noted that tolerability was within acceptable limits. 

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Next Steps Will Compare Immunotherapy Regimens 

An ongoing phase 3 trial named DREAM3R will investigate survival differences between chemoimmunotherapy regimens alongside chemotherapy or immunotherapy alone. The chemoimmunotherapy arm involves a platinum drug and Keytruda with durvalumab (Imfinzi), an anti-PD-L1 antibody. 

“Hopefully, this study will accrue quickly, and we can get a definitive answer to the question of which is better: chemoimmunotherapy or ipilimumab and nivolumab,” Baik said. The U.S. Food and Drug Administration approved the immunotherapy drugs nivolumab (Opdivo) and ipilimumab (Yervoy) as a first-line treatment for unresectable pleural mesothelioma. 

While epithelioid patients may not benefit as significantly from immunotherapy, a subgroup of patients may benefit from certain combinations. Challenges remain in finalizing FDA approval for more immunotherapy options, but clinical trials continue to evolve, and patient outcomes will keep improving. 

Baik said patients should be offered these multimodal treatments because the results are evident. 

“They’re clearly better than chemotherapy alone, so patients should be offered an immunotherapy approach,” she noted. “Of course, chemoimmunotherapy is not yet approved by the FDA, but it is an active option for patients.”

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