Inaccurate Lab Tests Might Lead To Inappropriate Treatment Of Breast Cancer

Main Category: Breast Cancer
Article Date: 07 Jan 2008 - 7:00 PDT

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Thousands of breast cancer patients might receive improper medications as a result of inaccurate results for two laboratory tests used to determine the most effective treatments for specific patients, the Wall Street Journal reports. According to the Journal, pharmaceutical companies are "trying to develop more medicines tailored to the individual characteristics of patients and their diseases," but recent studies that have found "problems in testing point to a potential snag for such drugs: They depend on accurate lab results."

The tests used to determine the most effective treatments for specific breast cancer patients are "less straightforward than many traditional lab procedures" and "require pathologists to make judgment calls after looking at tissue through a microscope, rather than giving simple yes-or-no answers," the Journal reports. One of the tests determines whether breast cancer patients have excessive amounts of the protein Her-2 present in their tumors, an indication that they would benefit from Herceptin, manufactured by Genentech.

The second test determines whether breast cancer patients have cell proteins that serve as receptors for estrogen and progesterone -- which can help tumors grow -- an indication that they would benefit from tamoxifen to suppress or block the hormones.

Study
A 2006 study conducted by Genentech examined test results from local labs nationwide and found that the labs reported false positives for Her-2 tests 14% to 16% of the time and reported false negatives 18% to 23% of the time. In addition, the College of American Pathologists and the American Society of Clinical Oncology estimate that labs might report inaccurate results for Her-2 tests 20% of the time.

Allen Gown, chief pathologist of PhenoPath Laboratories, said, "If we tried to market pregnancy tests with this rate of inaccuracy, they would be taken off the market," adding, "It means there are a lot of women being treated inappropriately."

According to the Journal, concerns about the accuracy of the tests "could add momentum to efforts by Congress and consumer groups to push for increased oversight over the lab-testing business, which is booming because of factors such as the rise in genetic testing and the aging of the baby boom generation." CMS, which regulates labs, has required them to demonstrate proficiency in 83 types of tests since 1992.

Barry Straube, chief medical officer at CMS, said that the agency might add to the list of additional tests, such as those used to determine the most effective treatments for specific breast cancer patients (Wilde Mathews, Wall Street Journal, 1/4).

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