| Mesothelioma Diagnosis Improved by New Tests |
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A combination of two genetic tests is more sensitive at distinguishing mesothelioma from normal cells than either test alone, according to a new study in the journal Cancer Cytopathology.
Mesothelioma can be difficult to diagnose, in part because its cells closely resemble other types of cancerous and non-cancerous cells. For example, normal cells from the lung lining that have become irritated can look very similar to mesothelioma.
Cytology—a technique that looks at the structure and properties of cells—is one method used to diagnose mesothelioma. The advantage to this technique is that it can be performed from fluid that is easily removed from a patient’s body, without the need for invasive surgery. Yet cytology is not always accurate. It often has false-negative results. Researchers have been looking for new ways to improve its sensitivity.
Investigators at Brigham and Women’s Hospital in Boston wanted to determine whether the combination of two genetic tests, used together with cytology, might be more precise than either test alone for diagnosing patients who are suspected of having mesothelioma. The first genetic test, called karyotyping, analyzes the cell’s chromosomes to look for evidence of cancer. The second, called fluorescence in situ hybridization (FISH), uses fluorescent tags to look for specific segments of DNA in cells.
The researchers examined fluid taken from the space outside the lungs and abdominal cavities (pleural and peritoneal effusions) of 48 patients who were suspected of having mesothelioma. When they performed FISH together with karyotype analysis, the researchers discovered that the combination of tests almost doubled the sensitivity—to nearly 60%.
“I think this would be useful in the initial diagnosis of mesothelioma. It might also be useful in patients who have been treated, to see whether they still have the disease,” says study author Rachel Factor, MD, a former fellow in the Brigham and Women’s Hospital Department of Pathology, and currently an instructor of Pathology at Boston Medical Center. Radiation or chemotherapy treatment can alter cells, causing them to look like mesothelioma, and making it more difficult for doctors to determine whether treatment has actually eradicated the cancer. The test also could be helpful for diagnosing patients who are unable to undergo surgery, according to Dr. Factor.
This study indicates that combining karyotyping and FISH can improve the sensitivity of current cytologic methods for diagnosing mesothelioma; however the test is far from perfect. Even when karyotyping and FISH are combined, they still result in a large number of false-negative results. The sensitivity could be improved if researchers used additional FISH probes, but many of these probes are not yet commercially available. Additional research will help fine-tune the test, but for now, just knowing that the combination of karyotyping and FISH effectively detects mesothelioma from fluids is promising, Dr. Factor says.
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