New “Real World” Study of Immunotherapy for Peritoneal Mesothelioma

A new study from one of the nation’s top cancer centers supports the role of immunotherapy in peritoneal mesothelioma treatment.

Immunotherapy is a treatment approach that aims to harness the body’s natural defense system to fight cancer. 

Several immunotherapy drugs have been tested for pleural mesothelioma. Pleural mesothelioma affects the lungs. Last year, the FDA approved a new combination of immunotherapy drugs for the pleural form of asbestos cancer. 

But there is less data on immunotherapy for peritoneal mesothelioma. Researchers at MD Anderson Cancer Center just released their findings on a class of immunotherapy drugs called immune checkpoint inhibitors (ICIs). They say it is the first “real-world evidence” of clinical outcomes with ICIs in peritoneal mesothelioma patients.

Immune Checkpoint Inhibitors for Mesothelioma

Peritoneal mesothelioma starts when cells in the lining of the abdomen (peritoneum) turn cancerous. Exposure to asbestos is almost always the cause. Scientists are still trying to understand why some people are more susceptible to the toxic effects of asbestos. 

Peritoneal mesothelioma cells try to shield themselves from immune system attack by expressing protective proteins. PD-1 is one such protein. Immune checkpoint inhibitors inhibit this mechanism. Keytruda, Yervoy, and Opdivo are examples of ICIs. 

This kind of immunotherapy for peritoneal mesothelioma is not as well-studied as it is in pleural mesothelioma. The aim of the MD Anderson study was to determine how well ICIs work against advanced peritoneal mesothelioma. 

The study is a “real world” investigation. Researchers analyzed the impact of immunotherapy for peritoneal mesothelioma patients who were not screened for particular criteria. The study included every advanced peritoneal mesothelioma patient treated with ICIs at MD Anderson between 2016 and 2020.

Results of Immunotherapy for Peritoneal Mesothelioma

There were 29 patients in the new study. Fifteen of them were women. Their median age was 60. The oldest patient was 77. 

Twenty patients had combination Yervoy/Opdivo immunotherapy for peritoneal mesothelioma. This is the same combination approved by the FDA for pleural mesothelioma. Nine patients had a single ICI. 

In sixty-five percent of patients, their tumors either shrunk or remained stable. This lasted for a median of 5.5 months. But for 14 percent of patients, it took a full year for their tumors to start growing again. 

Sixty-eight percent of patients on immunotherapy for peritoneal mesothelioma were still alive a year later. The median overall survival was a year and seven months. The longest living patient on this therapy lived for three years and seven months. Only one patient discontinued treatment because of toxicity. There was no major difference in the outcomes between combination and single-agent immunotherapy for peritoneal mesothelioma. 

The researchers say the next step is larger clinical trials. They want to come up with ways to predict which patients will respond to immunotherapy for peritoneal mesothelioma. 

“There is a critical need for dedicated trials and larger cohorts to define biomarkers of response or resistance, early referral to clinical trials, and novel combinatorial strategies to enhance responses and outcomes for patients with MPeM,” the report concludes. 

Source: 

Raghav, K, et al, “Clinical Efficacy of Immune Checkpoint Inhibitors in Patients With Advanced Malignant Peritoneal Mesothelioma”, Jama Network, August 2, 2021, https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2782760\