New York Times Examines Recent Research On Tests Determining Which Patients Should Receive Breast Cancer Drug Herceptin

New York Times Examines Recent Research On Tests Determining Which Patients Should Receive Breast Cancer Drug Herceptin

Recently released research has provided evidence that testing for breast cancer tumors that could be treated with Genentech's drug Herceptin could either be "highly inaccurate" or be using the "wrong cutoff values" to determine who should receive the drug, the New York Times reports (Pollack, New York Times, 6/12).

FDA in 1998 approved Herceptin for treatment of advanced HER2-positive cancer -- an aggressive form of the disease found in about 25% of breast cancer patients that involves extra copies of the HER2 protein -- that has spread beyond the breast. Some doctors began using the drug off-label in combination with chemotherapy to treat early stage patients after a 2005 study found positive results for such treatment. FDA in November 2006 expanded approval of Herceptin to include the treatment of a type of breast cancer when it has not spread beyond the breast or lymph nodes in patients who have undergone a lumpectomy or mastectomy (Kaiser Daily Women's Health Policy Report, 11/20/06).

According to two studies presented at the American Society of Clinical Oncology meeting in Chicago last week, patients who were determined to be HER2-negative using two tests that gauge the amounts of the protein in breast cancer tumors benefited from Herceptin. Both studies re-examined tumor samples from previous clinical trials that found Herceptin, if used after a tumor is removed by surgery, reduces cancer recurrence by 50%.

According to the Times, the clinical trials enrolled only patients that local laboratories determined had HER2-positive tumors, but the re-examination showed that as many as 20% of the tumor samples actually were HER2-negative. Women who had HER2-negative tumors also had a reduced risk of cancer recurrence after taking Herceptin, according to the studies.

Soonmyung Paik, who presented one of the studies at the conference, said that about 40% of women enrolled in his study had intermediate levels of HER2 that are classified as HER2-negative tumors under current guidelines. He said such women might benefit from Herceptin use. "To me, the take-home message is that we don't have a perfect test, unfortunately," Paik said.

Some experts were "skeptical" about the findings, saying that the studies were not large enough to make concrete conclusions and that it is unclear whether the tumors were truly HER2-negative because they had been tested by a local laboratory, the Times reports. Daniel Hayes -- a breast cancer specialist at the University of Michigan, who helped develop guidelines for HER2 testing -- said that the studies shed light on the inconsistent quality of HER2 testing in small laboratories. He said Herceptin should not be given to HER2-negative women because the drug is costly and raises the risk of heart failure.

James Doroshow of the National Cancer Institute, in a commentary after one presentation at the ASCO meeting last week, said that the studies have "major practice-changing potential" but added that the data are too preliminary to change treatment guidelines. Pamela Klein, an executive at Genentech, said the company is researching how best to identify patients eligible for the drug (New York Times, 6/12).

source : www.medicalnewstoday.com