‘Arbitrary’ Standards Used in Breast Cancer Tests
"Arbitrary standards" used to determine the outcome of a test performed on breast cancer patients could lead some women to fail to receive treatment to prevent recurrence of the disease, the Washington Post reports. Each year, about 200,000 breast cancer patients undergo a test that measures the "estrogen receptor status" of tumors. About 70% of breast cancers are "estrogen-receptor positive," meaning that the cancer cells have estrogen receptors and the patients can be treated with the drug tamoxifen, which minimizes the chances of recurrence. Women whose tumors do not have the receptors do not benefit from tamoxifen, however, so "doctors generally do not prescribe the drug for them," the Post reports. Over the last decade, laboratories have developed a new technique for conducting the receptor test, but many labs use "arbitrary cutoffs" for determining whether test results are positive or negative, according to a new study from Baylor College of Medicine.
The study revealed that although pathologists may classify test results as positive if as few as 1% of tumor cells show a color change, many medical laboratories require 10% to 20% of cells to show a change before giving a positive result. D. Craig Allred, a professor of pathology at Baylor, predicted that if most U.S. laboratories use a 10% cutoff for judging a test to be positive, about 5% of breast cancer patients -- about 10,000 patients a year -- will be misclassified as estrogen-receptor negative when they are actually estrogen-receptor positive and would benefit from tamoxifen therapy. Allred added that standards used to determine test results vary from laboratory to laboratory, and sometimes even among pathologists at the same hospital. "Quite frankly, many pathology laboratories don't have any business doing these tests. They don't know how," Allred said.
Both "false positive" and "false negative" test results carry potentially harmful consequences. Women with false positive results do not benefit from tamoxifen, but could experience an increased risk of uterine cancer and other side effects, such as blood clots, as a result of receiving the drug. But the "biggest concern" with the way the test results are determined, C. Kent Osborne, professor of medicine at Baylor said, is that women with "falsely negative" results will not be offered tamoxifen. Daniel Hayes, clinical director of the breast cancer program at Georgetown University's Lombardi Cancer Center, added that the lack of uniform standards "creates uncertainty about the proper treatment for some patients." However, Stuart Schnitt, director of surgical pathology at Beth Israel Deaconess Medical Center, stated that problems with the test "rarely" affect patient care. "I think [interpreting test results] is only a problem in a very small minority of cases," he said. Schnitt added that many pathologists know that certain types of breast tumors typically test positive or negative, and can retest cases in which "an unexpected result occurs."
Allred called for the adoption of uniform standards for interpreting test results, but added that women undergoing treatment for breast cancer should ask questions about how their estrogen receptor tests are performed and evaluated. Osborne added that women could also ask their physicians to send the test to another laboratory to be retested. However, he warned, the cost of repeating the test ranges from $100 to $150 and might not be covered by insurance. "Some hospitals make the decision on which antibody to use based on cost. That's ridiculous for a test as important as this. ... It could make the difference between getting (or not getting) a drug that could save your life," Osborne concluded (Okie, Washington Post, 12/4).This is part of the California Healthline Daily Edition, a summary of health policy coverage from major news organizations. Sign up for an email subscription.