Breast Cancer Patients Could Receive Wrong Treatment Because Of Errors In Widely Used Lab Tests

Main Category: Breast Cancer
Also Included In: Public Health
Article Date: 08 Jan 2008 - 7:00 PDT

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The Wall Street Journal on Friday examined the efficacy of two diagnostic tests used to determine which drugs to prescribe women with invasive breast cancer. According to the Journal, thousands of women with breast cancer might be receiving the wrong treatment because of errors in the two tests predominantly used to determine which drugs to prescribe. The test requires pathologists to make subjective calls after analyzing tissue with a microscope, the Journal reports.

One test examines whether a woman's tumor cells have too much of the HER2 protein. If the cells do contain too much HER2, patients are prescribed Genentech's drug Herceptin. The other test checks for the presence of cell proteins that act as receptors for the hormones estrogen or progesterone, the Journal reports. If the cell proteins are detected, physicians usually prescribe drugs such as tamoxifen, which blocks the production of the hormones.

According to the Journal, recent studies have found that there is a "potential snag" for these cancer-fighting drugs -- which drug should be prescribed depends upon accurate lab tests. Both pathologists and oncologists said labs inexperienced in a particular test might not understand how small variations in procedure -- such as how much tissue samples are heated and what preservative is used -- can impact results. Lee Newcomer, senior vice president of UnitedHealth Group, said, "We all make the assumption that every test is done well. It turns out it's not a correct assumption." Several private insurers -- including UnitedHealth, Aetna and WellPoint -- say that in general, they will pay for second-opinion breast cancer tests. However, Newcomer said that even though UnitedHealth covers a second test, few physicians order them.

In addition, a study published in 2006 and led by researchers at Genentech on HER2 tests found that 14% to 16% of women judged to be HER2-positive actually were negative for the protein. Of the women said to be negative, 18% to 23% were actually HER2-positive, the study found. The American Society of Clinical Oncology estimates that around 20% of HER2 testing might be inaccurate. In a separate study published online in August 2007 in the Journal of Clinical Oncology, researchers examined the accuracy of labs in various countries. The study found that 70% of 105 women who initially tested negative for the protein that acts as a receptor for estrogen were found to be positive when the tissue was retested by an experienced lab, while the positive tests were almost always correct.

Barry Straube, chief medical officer at the Centers for Medicare and Medicaid Services, said the agency is examining stricter quality-control requirements. Labs currently must pass outside proficiency checks on 83 types of tests, which do not include tests for breast cancer, the Journal reports. CMS is "considering adding additional tests," Straube said, adding the two breast cancer tests are likely candidates. The College of American Pathologists also plans to require proficiency checks this year from the labs it oversees that offer the HER2 test (Mathews, Wall Street Journal, 1/4).

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