A new report says the prognostic role of BAP1 expression in mesothelioma is not as cut-and-dried as some studies suggest.
Italian researchers analyzed the cases of 698 patients with pleural mesothelioma. The group included 60 of their own patients and another 638 from other studies.
Their analysis suggests that mesothelioma prognosis has more to do with subtype than with genetic BAP1 expression. They caution doctors not to put too much stock in a patient’s BAP1 status without also considering other factors.
Genetic Alterations and Mesothelioma Survival
Asbestos exposure is the primary cause of mesothelioma. But not everyone who is exposed to asbestos gets cancer. This may have to do with their genetic makeup.
Certain genetic alterations may make a person more susceptible to mesothelioma and other cancers. One of these genetic alterations is low or non-existent BAP1 expression.
BAP1 stands for BRCA1 associated protein-1. People who have an inherited BAP1 gene mutation produce less of the protein. This seems to increase their risk for malignant mesothelioma. People with this condition are also more prone to develop moles called atypical spitz nevi and a rare type of eye cancer.
Many people with a loss of BAP1 expression never even know it. Gene testing is not routine. Doctors cannot tell with an examination which patients have BAP1 loss.
BAP1 Expression and Mesothelioma Prognosis
Scientists disagree about the importance of BAP1 expression in mesothelioma prognosis. Some studies suggest that mesothelioma patients with BAP1 loss may be more responsive to certain kinds of treatments.
A 2019 German study suggested that the protein could also help doctors distinguish mesothelioma from other conditions.
But the new Italian study shows BAP1 expression is not a good tool for predicting mesothelioma outcomes.
Among the 60 study subjects at their hospital, 62 percent showed BAP1 loss. Most of these patients had the epithelioid mesothelioma subtype. Epithelioid mesothelioma tends to respond to treatment better than other subtypes.
Mesothelioma Survival is Multifactorial
The study subjects with BAP1 loss survived for a median of 14 months. This was about four months shorter than those with normal BAP1.
But those figures did not tell the whole story. When the researchers considered all the risk factors, they found no survival difference between mesothelioma patients with normal or BAP1 expression and those with BAP1 loss.
“Similarly, the meta-analysis consisting of 698 patients showed no difference in terms of overall survival according to BAP1 status,” writes lead author, Dr. Luca Cantini. The researchers conclude that BAP1 expression by itself cannot predict mesothelioma prognosis.
“BAP1 expression is not an independent prognostic factor for malignant pleural mesothelioma patients and it should not be considered without taking into account tumor histotype,” the report concludes.
Dr. Cantini says future research should focus more on the role of BAP1 expression in new kinds of mesothelioma immunotherapy.
Cantini, L, et al, “Questioning the Prognostic Role of BAP-1 Immunohistochemistry in Malignant Pleural Mesothelioma: A Single Center Experience With Systematic Review and Meta-Analysis”, June 21, 2020, Lung Cancer, Epub ahead of print, https://www.lungcancerjournal.info/article/S0169-5002(20)30498-0/pdf