Checkpoint inhibitor immunotherapy works for malignant mesothelioma, specifically when the disease forms near the lungs.
There’s another type of mesothelioma, usually understudied and overlooked, left out of this discussion. New research aims to provide confidence that immunotherapy for mesothelioma can help these patients as well.
The Rutgers Cancer Institute of New Jersey hosted a study on the efficacy of immune checkpoint inhibitor drugs for peritoneal mesothelioma. This type of mesothelioma forms in the peritoneum, the thin lining surrounding the abdominal cavity.
It’s much rarer than pleural mesothelioma near the lungs. There are fewer than 1,000 peritoneal mesothelioma cases per year, which makes clinical studies and reviews much tougher.
Dr. Richard Alexander, chief surgical officer and chief of surgical oncology at Rutgers Cancer Institute, and his team found some answers.
Results From the Rutgers Cancer Institute Study
The purpose of the study was to determine if peritoneal mesothelioma tumors express high levels of the PD-L1 protein. This protein subdues the immune system by engaging T-cells through the PD-1 receptor.
Some immune checkpoint inhibitor drugs, like Keytruda and Opdivo, block the PD-L1 pathway. These drugs allow the immune system to operate as normal, seeking and attacking unwanted diseases like mesothelioma.
Oncologists and mesothelioma specialists know from years of data that PD-L1 is highly expressed in most pleural mesothelioma cases. Dr. Alexander confirmed similar findings for peritoneal mesothelioma.
According to the report on the Rutgers Cancer Institute website, the team identified 24 samples from 20 peritoneal mesothelioma patients evaluated and treated at the hospital within the past three years. They used a PD-L1 stain (Dako 22c3) to reveal the protein in samples.
From the 24 samples, 19 were above the threshold for PD-L1 overexpression — more than 75% of the samples.
They also learned that PD-L1 overexpression is an indicator of poorer survival. As the threshold for PD-L1 overexpression increased, survival times dropped:
- The median survival for the 20 patients was 110 months (around nine years).
- At higher thresholds, PD-L1-overexpressed cases had a median survival of just 49 months.
What Does This Mean?
Peritoneal mesothelioma patients have two primary treatment options: surgery or chemotherapy. Surgery offers the best hope for long-term survival, but many patients aren’t candidates. They’re often left with chemotherapy alone, which has uncomfortable side effects and modest survival benefits.
Dr. Alexander’s findings reveal a promising option: immunotherapy. Checkpoint inhibitors generally have fewer side effects than chemotherapy and have improved survival for pleural mesothelioma patients.
The same could be true for the small subset of people with peritoneal mesothelioma.
“Our plan will be to test checkpoint inhibition in patients prospectively to determine whether or not it is associated with significant antitumor activity,” Dr. Alexander wrote.
For more information on immune checkpoint inhibitors or other immunotherapy drugs, contact our patient advocate Karen Ritter at karen@mesotheliomaguide.com to discuss possible clinical trials for peritoneal mesothelioma patients.
Sources & Author
- Exploring PD-L1 Expression in Malignant Peritoneal Mesothelioma. Rutgers Cancer Institute of New Jersey. Retrieved from: https://cinj.org/exploring-pd-l1-expression-malignant-peritoneal-mesothelioma. Accessed: 03/24/2021.
- 69: Expression of PD-L1 in Patients With Malignant Peritoneal Mesothelioma (MPM). National Library of Medicine. Retrieved from: https://pubmed.ncbi.nlm.nih.gov/35489218/. Accessed: 07/11/2023.
