Pleural Mesothelioma Patients with 5-Year Survival Still Rare

Although no amount of asbestos exposure is considered safe, lower levels of non-occupational exposure are most often linked to long-term survival for those diagnosed with malignant pleural mesothelioma, according to a recent study.

Clinical Lung Cancer published the study that compared characteristics of 43 pleural mesothelioma patients who survived at least five years with the disease to a much larger control group.

Several previous mesothelioma studies have estimated that the five-year survival rate is just under 5% for pleural mesothelioma, an aggressive cancer with no definitive cure. It is caused almost exclusively by exposure to asbestos.

“The reasons for dismal long-term survival rates include diagnosis at late stage and poor response to conventional treatment modalities,” the authors wrote. “However, as some patients achieve prolonged survival, researchers have tried to identify prognostic factors underlying this phenomenon.”

Age, Sex and Exposure Matter in Mesothelioma Survival

Clinical factors of long-term survival were not surprising, and similar to less comprehensive studies. They included younger patients, more frequently female patients, a better performance status at the time of diagnosis and non-occupational exposure to asbestos.

The study was conducted by researchers mostly from the departments of pathology and pulmonary medicine at Helsinki University Hospital in Finland.

Researchers declined to provide additional perspective and insight to The Mesothelioma Center at Asbestos.com.

The original aim of the study was to evaluate diagnostic accuracy of long-term mesothelioma survivors, which often is questioned with this tough-to-diagnose cancer.

“Our hypothesis was, similar to an earlier study conducted with patients with pancreatic cancer, that not all of these [long-term survival] patients would represent mesothelioma, but rather had been misdiagnosed,” the authors wrote. “But contrary to our original hypothesis, the re-evaluation confirmed good diagnostic accuracy, suggesting a subtype with a better prognosis.”

The study also concluded that tumor size and first-line treatment were associated with survival time.

Finnish Study Included Epithelial Subtype

The study originated from a cohort of 1,010 patients from the Finnish Cancer Registry who were diagnosed with pleural mesothelioma. A subgroup of 43 long-term survivors were compared with a control group of 84 patients, all of whom had the most easily treated epithelial subtype of mesothelioma.

Smoking History Similar with Both Study Groups

Although smoking has been associated typically with shorter mesothelioma survival rates, it was not a factor in either group of patients in this study. In the long-term survival group, 44% said they had never smoked. In the control group with the much shorter median survival, 48% said the same.

Occupational exposure was documented from medical records. In Finland, employees are automatically entitled legally to receive compensation for an occupational disease.

A second malignancy type was found in 16% of the long-term survival group and 17% of the control group. There was no difference observed in the first-line treatment modality between the two groups.

By the end of the study period, 10 patients in the long-term survival group were still alive and three had died of causes other than pleural mesothelioma. None in the control group were still alive.

“The prolonged survival time is most likely explained by a combination of tumor-, patient- and treatment-related factors,” the authors concluded. “Although we found that surgery and chemotherapy were associated with longer survival, the role of radical intent surgery was insignificant.”

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