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Immunotherapy and Chemotherapy Shrink Peritoneal Mesothelioma Tumors: New Case Reports

ByAlex Strauss

immunotherapy and chemotherapyTwo new case reports appear to support the idea that immunotherapy and chemotherapy can work together to fight peritoneal mesothelioma. 

The case reports appears in the newest issue of the Journal of Immunotherapy. It details the cases of two patients with malignant peritoneal mesothelioma – a lethal cancer of the lining of the abdomen. 

Both patients relapsed on standard platinum-based chemotherapy. But adding an immune checkpoint inhibitor dramatically improved their results. In one case, a patient’s tumor nearly disappeared. 

Doctors at New York’s Memorial Sloan Kettering Cancer Center say the cases suggest that immunotherapy and chemotherapy might offer an alternative for patients who have run out of options. 

Alternative Treatments Needed for Peritoneal Mesothelioma

About a fifth of patients who get mesothelioma have the peritoneal variety. Peritoneal mesothelioma tumors start on the membrane that surrounds the abdominal organs. Nearly all mesothelioma patients have a history of asbestos exposure. 

Once peritoneal mesothelioma takes hold, it is very hard to stop. The combination of immunotherapy and chemotherapy is a new approach for peritoneal mesothelioma. Right now, most patients undergo chemotherapy. Those who are healthy enough may also have surgery. 

Alimta is the main chemotherapy drug for mesothelioma. It is usually combined with a platinum drug like cisplatin or carboplatin. But, for most patients, the combination eventually stops working and their mesothelioma tumors come back. 

There is no standard second-line mesothelioma treatment in these cases. But the authors of the new case reports say the success of their patients shows that immunotherapy and chemotherapy can work together – for the right patients. 

Combining Immunotherapy and Chemotherapy for Better Results

In the two new case reports, patients relapsed after the gold standard peritoneal mesothelioma treatment: cytoreductive surgery and chemotherapy. Both patients had the standard combination of Alimta (pemetrexed) and a platinum drug. 

After they relapsed, their doctors decided to try immunotherapy and chemotherapy together. Both patients received the immune checkpoint inhibitor (ICI) pembrolizumab (Keytruda). 

Dr. Michael Foote, lead author of the paper, writes that both patients “possessed tumors without validated biomarkers of ICI response.” In other words, there was no clear indication that the combination of immunotherapy and chemotherapy would work. But it did. 

“In both cases, addition of pembrolizumab to platinum and pemetrexed treatment resulted in a substantial partial and a near complete disease response,” writes Foote. 

Foote says each patients’ “unique genomic landscape” likely contributed to their positive response. Having chemotherapy prior to immunotherapy probably also “primed” the tumors to be more responsive. 

The team concludes that the good results from immunotherapy and chemotherapy are enough to warrant further study in a larger group of peritoneal mesothelioma patients. 

Source: 

Foote, M, et al, “Treatment of Platinum Nonresponsive Metastatic Malignant Peritoneal Mesothelioma With Combination Chemoimmunotherapy”, November 1, 2021, Journal of Immunotherapy, Online ahead of print, https://journals.lww.com/immunotherapy-journal/Abstract/9000/Treatment_of_Platinum_Nonresponsive_Metastatic.99314.aspx

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