Mesothelioma Histology Impacts Response to Chemotherapy

Response to chemotherapy for people with malignant mesothelioma may depend – at least in part – on the histology or subtype of their tumor.

That is the finding of a new study from a team of Spanish doctors. The doctors analyzed the cases of 189 pleural mesothelioma patients treated at their hospital between 2002 and 2020. 

Their study confirms what other studies have suggested: People with epithelioid tumors have better response to chemotherapy than those with non-epithelioid subtypes. These patients experienced both longer progression-free survival and longer overall survival. 

Systemic Treatment for Pleural Mesothelioma

The first chemotherapy drug for malignant pleural mesothelioma received FDA approval in 2004. Alimta was the only approved systemic (whole body) treatment for pleural mesothelioma until 2020. 

In 2020, the FDA approved the immunotherapy drugs Yervoy and Opdivo for some mesothelioma patients. Most patients still start treatment with Alimta and a platinum drug (usually cisplatin or carboplatin). Unfortunately, response to chemotherapy varies widely among mesothelioma patients. 

Patients who respond well may have more rounds of chemotherapy if their cancer comes back. Patients who do not have a good response may try another type of treatment or a clinical trial. 

Because mesothelioma tumors grow so quickly, the ability to predict response to chemotherapy could be life-saving.

Predicting Response to Chemotherapy 

There are three main types of mesothelioma. Doctors classify them based on where they occur in the body. 

Pleural mesothelioma tumors grow on the membrane around the lungs. Peritoneal mesothelioma affects the lining of the abdomen. Pericardial mesothelioma tumors occur on the membrane around the heart. Pleural mesothelioma is by far the most common type.

Mesothelioma tumors can be further divided by the shape of the cells themselves. This is called the tumor histology. Epithelioid cells make up about 70 percent of mesotheliomas. Sarcomatoid cells are the most resistant to treatment. Biphasic tumors contain some of each kind of cell. 

Response to chemotherapy is usually better among people with epithelioid histology. The new report bears this out. Median progression-free survival for epithelioid patients treated with chemotherapy was 4.8 months. Non-epithelioid patients had a progression-free survival of 3.6 months. 

The improved response to chemotherapy meant epithelioid patients also lived longer. 

“Median OS [overall survival] of epithelioid patients treated with first line chemotherapy was 26.7 months versus 15.0 months in non-epithelioid patients.” writes lead study author Dr. Susana Cedres, an oncologist at the Hospital Universitari Vall d’Hebron in Barcelona. “In our series, patients with non-epithelioid tumors presented worse prognosis.”

Some of the epithelioid patients had longer progression-free survival if they had Alimta and cisplatin. But there did not seem to be a connection between mesothelioma subtype and response to chemotherapy with either cisplatin or carboplatin. 

Sources:

Cedres, S, et al, “Efficacy of chemotherapy for malignant pleural mesothelioma according to histology in a real-world cohort”, November 1, 2021, Scientific Reports, https://www.nature.com/articles/s41598-021-00831-4