Breast Cancer Gene Testing For Roches Herceptin Often Lacking
Two-thirds of women with invasive breast cancer had no documentation of having undergone testing for abnormalities on the HER2 gene that makes cancer more dangerous, according to a report in the journal Cancer. The article also found about 1 in 5 tests for HER2 done by local laboratories are inaccurate when compared with larger laboratory results on the same tissue.
Healthy breast cells contain two copies of HER2, according to the American Society of Clinical Oncology. About 20 percent of women with invasive breast cancer have extra copies, and these tumors, called “HER2-positive,” are aggressive forms of the disease that are more difficult to treat. The doctors group recommends that all patients with invasive breast cancer be tested to find out their HER2 status.
“Our review of the literature suggests that there are important knowledge gaps regarding the real-world use of HER2 testing” and Herceptin, said Elena Elkin, a researcher at Memorial Sloan-Kettering Cancer Center in New York and one of the studys authors, in a statement released by the journal.
Todays report reviews previously published studies to determine how testing is used in the clinic, and was led by Kathryn Phillips of the University of California, San Francisco.
Cancer Spread
Invasive breast cancer occurs when the cancer has spread beyond its initial point of origin, usually in the milk ducts or milk-producing glands, to other breast tissue. From there, it is easier for the disease to spread to other parts of the body, according to the Mayo Clinic. Invasive ductal carcinoma, which begins in the milk ducts, accounts for about 70 percent of all breast cancer, the Mayo Clinic says on its Web site.
For the 20 to 30 percent of patients who over-express HER2, Herceptin is “highly effective,” the authors wrote. Without the ability to target that population, the drug wouldnt have been approved, according to the report. Testing for the gene is important because withholding Herceptin from patients who may benefit from it may mean they miss an opportunity to reduce their risk of death.
Additionally, providing Herceptin to a woman without the abnormality exposes her to “an unnecessary risk of heart failure” as well as incurring a cost to the health-care system of $100,000 annually. About 1 in 5 women who were taking Herceptin had no proof of a test in their health insurance records, the review found.
Standardize Testing
“It is possible that a test had been performed and given a positive result but wasnt properly documented,” Elkin said in an e-mail.
The authors recommended the testing be standardized to help ensure it is provided to patients. More information on the technologies used for tests also may help, they said.
Herceptin isnt the only treatment approved for use in HER2 breast cancer. GlaxoSmithKline Plc.s Tykerb was also approved for that use in 2007, and some doctors recommend certain chemotherapy regimens, according to the Mayo Clinic.