Inaccurate Lab Tests Might Lead To Wrong Treatment of Breast Cancer

Armen Hareyan's picture

Thousands of breast cancer patients might receive impropermedications as a result of inaccurate results for two laboratory testsused 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 tailoredto the individual characteristics of patients and their diseases," butrecent studies that have found "problems in testing point to apotential snag for such drugs: They depend on accurate lab results."

Thetests used to determine the most effective treatments for specificbreast cancer patients are "less straightforward than many traditionallab procedures" and "require pathologists to make judgment calls afterlooking at tissue through a microscope, rather than giving simpleyes-or-no answers," the Journal reports. One of the testsdetermines whether breast cancer patients have excessive amounts of theprotein Her-2 present in their tumors, an indication that they wouldbenefit from Herceptin, manufactured by Genentech.

Thesecond test determines whether breast cancer patients have cellproteins that serve as receptors for estrogen and progesterone -- whichcan help tumors grow -- an indication that they would benefit fromtamoxifen to suppress or block the hormones.



A 2006 study conducted by Genentech examined test results from locallabs nationwide and found that the labs reported false positives forHer-2 tests 14% to 16% of the time and reported false negatives 18% to23% 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 ofinaccuracy, they would be taken off the market," adding, "It meansthere are a lot of women being treated inappropriately."

According to the Journal,concerns about the accuracy of the tests "could add momentum to effortsby Congress and consumer groups to push for increased oversight overthe lab-testing business, which is booming because of factors such asthe 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.

BarryStraube, chief medical officer at CMS, said that the agency might addto the list of additional tests, such as those used to determine themost effective treatments for specific breast cancer patients (WildeMathews, Wall Street Journal, 1/4).

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