Most Oncologists Feel New Genetic Test for Tamoxifen Sensitivity Not Ready for the Clinic
Despite commercial availability and direct to consumer marketing of a new genetic test designed to reveal a breast cancer patient’s sensitivity to tamoxifen, most physicians in the U.S. are not currently using it to guide treatment, according to research from Duke University Medical Center presented today at the CTRC-AACR San Antonio Breast Cancer Symposium.
"We found that even though 90 percent of all the oncologists we surveyed were aware of the test, only a third of them had ever ordered it and only 14 percent of them had used it for more than 10 percent of their patients on tamoxifen,” says Jeffrey Peppercorn, MD, an assistant professor of medicine at Duke and the lead author of the study.
Tamoxifen is a drug that can help prevent breast cancer recurrence, but it does not help all patients equally. Recent studies suggest that some of the differences may be linked to how women are able to metabolize the drug, which studies show may be linked to genetic differences in the CYP2D6 enzyme.
A test that reveals a patient’s genetic profile is commercially available. It costs several hundred dollars and is often covered by insurers.
Peppercorn and colleagues from Duke mailed surveys on CYP2D6 testing to all breast cancer oncologists identified at hospitals in the National Comprehensive Cancer Network (NCCN) and a sample of community-based oncologists. They evaluated knowledge and use of the test as well as patient demand for it.
201 of 459 (44 percent) of oncologists responded. While NCCN-based physicians were more likely than their community-based colleagues to be aware of the test (98 percent vs. 82 percent, respectively) and more likely to get requests from their patients for it (33 percent vs. 12 percent), community-based practitioners were about twice as likely to use the test in their practices.
"We found that most oncologists are not using this test. Greater specialization in breast cancer management and greater awareness of the emerging data for this new test corresponded to less likelihood of ordering the test and lower likelihood of changing practice based on test results," says Peppercorn.
"This is an important example of the need for further educational efforts and further research surrounding this and other new genetic tests that are frequently becoming commercially available ahead of the evidence on how they can best help patients."
There are alternatives to tamoxifen, but for premenopausal women tamoxifen remains the gold standard says Peppercorn.
"At this point, it is not entirely clear if using the test really improves outcomes. Post-menopausal women on tamoxifen should be aware that another class of drugs, aromatase inhibitors, are a widely-used and proven alternative. For pre-menopausal patients, it is reasonable to discuss this test with your doctor, but patients need to be aware that the jury is still out on any benefit the test may offer."
Data is expected soon from large randomized trials evaluating the potential for this test to determine the choice of treatment in postmenopausal women with breast cancer.
Peppercorn is also a co-investigator on studies in collaboration with colleague William Irvin and the University of North Carolina evaluating the potential for CYP2D6 testing to guide changes in tamoxifen dose to overcome genetic differences in metabolism that will be presented on Saturday and Sunday at the symposium.
Duke colleagues who contributed to the study include Erika Hamilton, Sunny Qiu, Isaac Lipkus, Kelly Marcom, Laura Beskow and Gary Lyman.