Peritoneal Mesothelioma Grading System Improves Prognosis

The first two-tier grading system for peritoneal mesothelioma has produced a significant subset of patients with an incredible median overall survival of nearly 12 years.

That pathology-based grading system should provide patients with a more accurate prognosis, potentially helping doctors design more personalized and effective therapies.

“We can tell patients now what the future holds. That's a big deal,” surgical oncologist Dr. Edward Levine, Comprehensive Cancer Center director at Wake Forest Baptist Health, told Asbestos.com. “We can now better prognosticate how our patients are likely to do.”

Levine, a specialist in peritoneal mesothelioma, was part of a medical team that recently studied database cases from the past 20 years, applying pathological analysis previously used only with pleural mesothelioma, which is more common.

The American Journal of Surgical Pathology published the findings in its September issue. Surgeons from Wake Forest, University of Mississippi Medical Center and Memorial Sloan Kettering Cancer Center joined Levine in the research.

A cancer grading system is different than a cancer staging system. The grade, which is based on cell appearance, is an indication of how quickly the cancer tumor it is expected to grow. The higher the grade, the faster it grows.

Meanwhile, staging of a tumor is based on its extent or size. The higher the higher the number, the more advanced the cancer.

Wide Range of Mesothelioma Survival Rates

Researchers used 46 cases of the epithelioid subtype of mesothelioma in the study and divided them into low-grade and high-grade tiers based on characteristics found in the tumor cell nucleus.

The low-grade tier had an overall median survival of 11.9 years and a five-year survival rate of 57 percent. The high-grade tier had a median survival rate of 3.3 years and a five-year survival rate of 35 percent.

The low-grade tier had a median progression-free survival of 4.7 years and a five-year survival rate of 65 percent. The high-grade tier had a median progression-free survival of 1.9 years and a five-year survival rate of 35 percent.

“Not everyone is going to be a long-term survivor. I wish they all could be, but we're not there yet,” Levine said. “The patient with the worst prognosis might benefit from additional treatments. We don't know that yet, but it's something to think about.”

Levine is intrigued by the potential gains in therapy more exact prognostics could spark, but there are no assurances. All cases in the study included cytoreductive surgery and heated intraperitoneal chemotherapy (HIPEC), which are the standards of care today.

“These are new findings, so right now the diagnostics are ahead of the therapeutics a little bit,” he said. “That might change. I hope that it does.”

Mesothelioma Treatment Advances Widen Survival Gap

Pleural mesothelioma is a rare and aggressive cancer caused by inhalation of asbestos fibers that become lodged in the thin membrane around the thoracic cavity. Over time, those fibers cause scarring that can develop into cancer.

An estimated 3,000 people are diagnosed with mesothelioma annually in the U.S., but only 10 percent of those cases are the peritoneal type. Epithelioid is the most common subtype of pleural and peritoneal mesothelioma.

The recent study reinforced the growing length of survival gap between peritoneal and pleural mesothelioma patients.

Wake Forest School of Medicine's earlier study showed the median survival of a peritoneal mesothelioma patient was more than four times greater than of a pleural mesothelioma patient.

Some of the difference in survival between the two types stems from therapeutic advancements available to peritoneal patients. The HIPEC procedure has worked well, but it is less effective for pleural mesothelioma.

Although the use of asbestos, a naturally occurring mineral, has dropped significantly across the country in recent decades, the rate of mesothelioma diagnosis remains steady.

It often takes 20-50 years after first exposure to asbestos before doctors diagnose the cancer. Exposure today often comes from the remodeling, renovating or demolishing older structures containing asbestos, which makes advances in diagnostics and therapeutics critical.

“We have patients now who are long-term, disease-free survivors. Some of it because of the treatment they received,” Levine said. “Some of it, obviously now, is because they were part of this subset of patients who had a better prognosis based on the nature of their disease.”

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