AboutMesothelioma.Net

By Wade Rawlins
Doctors often have difficulty distinguishing whether a patient has malignant mesothelioma, a cancer that affects the lining of the lung, or adenocarcinoma, a type of cancer that affects the lung itself. Increasingly, they have used sophisticated blood tests that involve various panels of antibodies to help diagnose malignant mesothelioma.

Antibodies are proteins that are produced as part of the body’s immune system reaction. They are produced to fend off or neutralize invading molecules of cold germs and diseases. Clinicians use antibodies to identify or “tag” the specific antigens that indicate tissue changes consistent with mesothelioma or other diseases. For example, elevated amounts of the PSA antibody are a signal of possible prostate cancer in men so after a certain age men routinely have a PSA test when they get a physical. The antibodies are identified in laboratory blood tests.

Yet, there is no overall consensus as to which cocktail of antibodies is best at predicting the presence of mesothelioma. The lab tests are somewhat costly, so there is a need for development of consensus on guidelines for standardized antibody tests for the diagnosis of malignant mesothelioma. It could help reduce diagnostic errors and cost.

Recognizing this knowledge gap, researchers at Cedars-Sinai Medical Center in Los Angeles reviewed hospital medical records and identified 153 patients that were diagnosed from 2005 to 2007 with malignant epithelioid cells in pleural effusions, the excess fluid in the sac that encases the lungs and causes shortness of breath and chest pain. They analyzed the profile of antibodies and antigens of each malignant pleural effusion and correlated it with the various disease diagnoses. Their aim was to evaluate which antibodies were most predictive.

Currently, the number of antibodies analyzed by a lab to make a diagnosis varies widely. Some cell pathologists use just one or two antibodies per case to focus on the most probable diagnosis in a case. Others cast a wide net and employ more than 20 antibodies to test for every possible diagnosis to provide a comprehensive (and more costly) work-up. A maximum of 31 different immunohistochemical tests had been used by cell pathologists during the work up of the 153 cases examined by the researchers, with an average of 6 antibodies per case.

In an analysis of data published in Diagnostic Cytopathology, the researchers at Cedars-Sinai Medical Center said the anti-bodies that provided the best odds for specific diagnoses were TTF-1 for pulmonary carcinoma, calretinin for mesothelioma, ER and PR for breast carcinoma, CA125 for Mullerian, CDX2 for gastrointestinal origin of a carcinoma and PSA for prostatic carcinoma.

The antibody panels were able to diagnose correctly 77 percent of the malignant pleural fluid cell specimens from female patients and 50 percent of those from male patients.

The researchers said a systematic approach is needed to select gender specific anti-body panels to evaluate pleural cytology specimens with malignant epithelioid cells. They said their results would need to be confirmed with other tests using larger sample sizes. But they said their preliminary results do suggest that the antibody panels have significantly better predictive value than ad hoc panels selected by individual cell paththologists. They said the use of two anti-body panels tailored to the patient’s gender for the incidence of various tumors provides a cost-effective and sensitive method for the initial work-up of the cases.

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