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Immunotherapy is a form of cancer treatment that uses a patient’s immune system to fight the disease. By manipulating the immune system as a whole or by utilizing components of the immune system, or cell proteins known as antibodies, doctors are able to target additional proteins that help cancer cells grow. The antibodies will bind to the targeted cancer cell proteins and will either stop the cancer cells from growing or will kill them.
A newer immunotherapy drug for mesothelioma patients known as pembrolizumab, or Keytruda, is showing promise as a successful treatment option. Made by the American pharmaceutical company Merck, Keytruda is an anti-PD-L1 drug that targets the PD-L1 protein expressed in mesothelioma types. About 20% to 40% of mesotheliomas express PD-L1 protein.1,2 Most sarcomatoid type of mesotheliomas expressed PD-L1.2'
Dr. Evan Alley from University of Pennsylvania presented early results of the Phase 1b clinical trial that investigated Keytruda’s effect on mesothelioma patients at the recent American Association for Cancer Research meeting in Philadelphia.
Twenty-five patients with pleural malignant mesothelioma were treated with Keytruda. As this was the first clinical trial, each mesothelioma expressed the PD-L1 protein and all patients had been treated with at least standard chemotherapy.
PD-L1 Expression and Survival Statistics
Patients with PD-L1 positive mesotheliomas on average have a short overall survival time of about 5 months. Patients with mesotheliomas that do not express PD-L1 have on average a significantly longer survival time— about 14 months.
Early Trial Results Appear Promising
After 5 and ½ months, pembrolizumab treatment had helped about 3 of every 4 mesothelioma patients in this trial. About half of the tumors stopped growing (48%) and about 1 in 4 mesotheliomas shrank at least 30%. Physicians called the side effects as manageable, especially in comparison to the side effects of chemotherapy.
New Clinical Trial is Recruiting
A follow-on clinical trial sponsored by University of Chicago and National Cancer Institute is recruiting patients. They are recruiting patients with mesothelioma regardless of PD-L1 expression. The patients will be treated with pembrolizumab. The trial number is NCT02399371.3
As with all clinical trials, it’s important to ask your physician questions about the potential risks and potential benefits of this therapy for your situation. For these types of therapies, it’s very important to be relatively healthy as patients with modestly poorer health did not benefit from checkpoint inhibitor therapies. Likewise, it’s also important to discuss the risks and potential benefits with your family before making a decision to join a clinical trial.
Cedres S, Ponce-Aix S, Zugazagoitia J et al. Analysis of Expression of Programmed Cell Death 1 Ligand 1 (PD-L1) in Malignant Pleural Mesothelioma (MPM). PLoS One 2015;10(3):e0121071.
Mansfield AS, Roden AC, Peikert T et al. B7-H1 expression in malignant pleural mesothelioma is associated with sarcomatoid histology and poor prognosis. Journal of Thoracic Oncology 2014;9(7):1036-1040.
Pembrolizumab in Treating Patients With Malignant Mesothelioma https://clinicaltrials.gov/ct2/show/NCT02399371 acc.: June 2,2015 (2015).