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Long-Term Peritoneal Mesothelioma Survival with Apitolisib

There is hopeful news this week about the survivability of peritoneal mesothelioma, particularly when relapses are treated with a powerful drug called apitolisib.

Peritoneal mesothelioma is a less common form of the rare asbestos-related cancer, malignant mesothelioma. It starts on the membrane that surround the abdominal organs and can quickly spread throughout the abdomen.

According to the National Cancer Institute, the one-year survival rates for both peritoneal mesothelioma and the more common pleural mesothelioma is about 40 percent.

Understanding Apitolisib

But researchers in Surrey, England are reporting two cases of long-term peritoneal mesothelioma survival in women who were treated with apitolisib, a drug that inhibits important cell signaling pathways.

The P13K (phosphoinositide 3-kinase) and mTOR (mammalian target of rapamycin) pathways help regulate the cell cycle and are directly related to cell proliferation, cancer, and longevity.

Apitolisib can interrupt these pathways inside cancer cells, making it harder for certain kinds of mesothelioma tumors to grow unchecked.

Encouraging Mesothelioma Results

In a report published in ESMO Open, the online-only, peer-reviewed, open access journal of the European Society for Medical Oncology, researchers with the Royal Marsden NHS Foundation Trust and the Institute of Cancer Research suggest that, in the right patients, apitolisib could dramatically extend peritoneal mesothelioma survival.

The report describes the cases of two young women with with a slow-growing or “indolent” form of papillary peritoneal mesothelioma. Both women eventually relapsed after undergoing standard chemotherapy with pemetrexed (Alimta) and cisplatin.

But the researchers say the patients experienced “symptomatic and disease benefit” with apitolisib, with one patient having a partial response for almost 3 years. Both mesothelioma patients are still alive at 10 and 13 years from diagnosis.

“These case presentations highlight a subgroup of rare MPeM that behave indolently that is compatible with long-term survival,” writes lead author Saoirse Dolly with the Royal Marsden NHS Foundation Trust. “This series identifies the use of targeted therapies with PI3K-mTOR-based inhibitors as a novel approach, warranting further clinical assessment.

It is important to note that the peritoneal mesothelioma patients whose cases are detailed in this report had received genetic testing  and had been found not to have certain key mutations.

The researchers say they hope the report will “encourage recruitment of peritoneal mesothelioma patients to early phase clinical studies.

Despite heavy regulation of asbestos in the US, about 2,500 people are diagnosed with malignant mesothelioma each year.


Dolly, S, et al, “Indolent peritoneal mesothelioma: PI3K-mTOR inhibitors as a novel therapeutic strategy”, April 12, 2017, ESMO Open, eCollection 2017

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