Understanding Peritoneal Mesothelioma Life Expectancy

The International Mesothelioma Interest Group (iMig) conference, held every two years, brings together dedicated researchers who study all forms of mesothelioma, including peritoneal mesothelioma. Kazan Law, which sponsors the Mesothelioma Circle blog, is a supporter of this crucial research through its sponsorship of the Young Investigator Awards. These awards encourage the next generation of scientists to use their talents to help understand this deadly form of cancer.

At the 2018 iMig conference, one of these awards went to a group that studied the factors that affect life expectancy for peritoneal mesothelioma patients. This research seeks to fill a critical gap in medical understanding of this rare form of a rare cancer.

What is Peritoneal Mesothelioma?

The asbestos mineral naturally forms in tiny, spiky threads. It’s easy for invisible bits of these threads to become airborne when asbestos is handled. For decades, manufacturers used asbestos in their products without providing warnings or adequate protective gear to their employees and others who came in contact with toxic asbestos dust. Without realizing it, these people inhaled sharp asbestos bits. These bits can lodge in the lungs and cause pleural mesothelioma. Pleural mesothelioma tumors grow in the lining around the lungs.

Peritoneal mesothelioma forms in the peritoneum, the lining that surrounds the organs of the abdomen. Like the pleural form, peritoneal mesothelioma is caused by asbestos. When the fibers take a different route through the body, they may bypass the lungs and end up lodged in the abdomen.

Because the lungs are the first stop for inhaled asbestos, the pleural form of mesothelioma is by far the most common, making up more than three quarters of all mesothelioma cases. Peritoneal mesothelioma is the second most common form of this disease, but only about 10% of mesothelioma diagnoses are peritoneal mesothelioma.

Peritoneal mesothelioma requires different treatments than pleural mesothelioma. Surgical procedures are quite different. The systemic chemotherapy that is effective for the pleural form doesn’t do much to help peritoneal mesothelioma patients. The most effective mesothelioma chemotherapy is one that is commonly used for abdominal cancers. Called HIPEC, this chemotherapy circulates pre-heated drugs directly around the tumor.

When predicting life expectancy and the progression of the disease (the prognosis), doctors have used the same model for peritoneal mesothelioma patients as for pleural. They had no choice; no one had studied the prognosis of peritoneal mesothelioma to develop a predictive model. Until now.

Peritoneal Mesothelioma Prognosis

The study that won this iMig Young Investigator Award is a model of the kind of scientific exchange that the organization hopes to foster. The research team is led by David B. Chapel, from the pathology department at the University of Chicago Medicine. Other team members are affiliated with Cedars Sinai Medical Center in Los Angeles; Cardiff and Vale University, Wales, UK; Tokyo Women’s Medical University in Japan, and the University of Vermont Medical Center.

This international collaboration studied the medical histories of 102 peritoneal mesothelioma patients diagnosed between 1967 and 2016. Of these patients, 61 were women and 41 men. Using data about the patients and data from their test results, the study was able to draw some interesting conclusions about the prognosis for peritoneal mesothelioma.

The average age at diagnosis was 57, significantly younger than the average age at which pleural mesothelioma appears (early 70s). Perhaps partly because of this, the studies showed that average life expectancy for these peritoneal mesothelioma patients was also longer than the typical prognosis for mesothelioma. The median overall survival time was 16 months, with more than a quarter still alive after eight years. When the researchers looked just at patients diagnosed after 1995, the median survival time shot up to 52 months (more than 4 years) and almost half survived eight years or longer. That’s a snapshot of the positive effect of better diagnosis and treatments on survival times for peritoneal mesothelioma patients. The longest survival time among the patients studied by the researchers was almost 13 years.

This study took a deep look into patient medical records to find out what other factors in a peritoneal mesothelioma diagnosis could affect a patient’s prognosis. They found that, the older the patient was at the time of diagnosis, the shorter the average survival time. Women tended to live longer after diagnosis than men. Those with a history of asbestosis had worse outcomes than patients with no asbestos disease before their diagnosis.

Some of the findings of the study were no surprise. The earlier the tumor was caught, the longer the survival time. Those with epithelioid mesothelioma cell type did better than those with sarcomatoid or biphasic cells. Sarcomatoid mesothelioma is typically more aggressive and quicker to spread and biphasic tumors contain both sarcomatoid and epithelioid cells. Fortunately, epithelioid is much more common that the other two mesothelioma cell types.

Inflammatory stroma (swelling of the cells of the connective tissue that supports organs) was associated with shorter survival times for peritoneal mesothelioma patients. And, as other mesothelioma research has indicated, loss of the BAP1 gene, which reduces tumor growth and metastasis (spread) had a negative effect on long-term survival. Immunotherapy research on the BAP1 gene may offer hope to peritoneal mesothelioma patients with this pathology.

Overall survival times are averages; they can’t predict what a particular peritoneal mesothelioma patient will experience. Yet, understanding prognosis is vital to doctors and their patients. It helps physicians give patients an idea what to expect and may help guide treatment decisions.

This international research collaboration is a work in progress. At the iMig conference, the group invited more medical institutions to provide data on peritoneal mesothelioma cases, so they can develop an even more accurate picture of the prognosis of peritoneal mesothelioma. They will continue their research with support from the Young Investigators Award.

Young Investigator Awards for Mesothelioma Research

Immunotherapy research for mesothelioma and other cancers with poor prognoses has received most of the attention recently, both from the media and from the mesothelioma community. Drug manufacturers are rushing to develop new cancer drugs and some patients have experienced dramatic reductions in their tumors.

Studies like this attempt to develop a model for predicting patient outcomes after a peritoneal mesothelioma diagnosis aren’t as dramatic, but they are just as vital. Many of the scientific advances that result in improved life expectancy for mesothelioma patients happen in small increments. Improvements in surgical techniques, new ways to administer chemotherapy, and development of more effective combination therapies have all added to the quality of life for mesothelioma patients and the length of time they get to spend with their families.

By sponsoring the Young Investigator Awards at the iMig conference, Kazan Law continues its commitment to improving the lives of mesothelioma families. These awards recognize that progress happens on many fronts. Every study that increases knowledge about peritoneal mesothelioma pushes science one step further on the road to a cure.