Genetic Test Predicts Recurrence of Breast Cancer, Effectiveness of Chemotherapy
A new genetic test can help predict the recurrence risk for breast cancer patients and can aid doctors in determining whether chemotherapy would be useful or could be safely avoided, according to studies presented Thursday at the San Antonio Breast Cancer Symposium, the New York Times reports. The test, called OncotypeDX, measures the activity of 21 genes -- many of which have been linked to cancer cell growth or division -- and calculates a recurrence risk score. Calif.-based Genomic Health, which manufactures the test, is selling it for $3,460. The company said that because it performs all of the testing in its own laboratory, it does not need FDA approval (Pollack, New York Times, 12/11).
According to the Washington Post, experts say the test "marks one of the first tangible benefits of the massive effort to harness genetics to fight cancer" (Stein, Washington Post, 12/11).
Results for one of the studies, which was published on the New England Journal of Medicine Web site, originally were presented at last year's breast cancer symposium (New York Times, 12/11). For that study, researchers from Genomic Health and the National Surgical Adjuvant Breast and Bowel Project tested tumor samples from 668 women who participated in clinical trials in the 1980s.
The women, ages 30 to 70, had early stage breast cancer that had not spread and had been treated with tamoxifen, a drug that slows or stops the growth of new breast cancer cells. Without knowing the women's outcomes, researchers calculated recurrence scores for the tissue samples using the OncotypeDX test. Slightly more than half of the women had a low-risk score. Researchers found that among women who had a low recurrence score, almost 7% experienced a recurrence in the 10 years following the trial, whereas 30% of those who had a high score experienced a recurrence in that time period. Women with an intermediate recurrence score had a 14% relapse rate (American Health Line, 12/5/03).
Results from a separate study by the same researchers were presented at the conference last week. The study examined tissue from 651 breast cancer patients and found that those with the highest risk of recurrence, according to the OncotypeDX test, were "also more likely to respond to chemotherapy," the Wall Street Journal reports (Hamilton, Wall Street Journal, 12/13). Among patients at highest risk for recurrence, 40% who received only tamoxifen had a recurrence of cancer within 10 years, compared with just 12% who received both tamoxifen and chemotherapy. In the low-risk group, both patients who received chemotherapy and tamoxifen and those who received tamoxifen alone had a recurrence rate of about 5% (New York Times, 12/11).
Overall, chemotherapy reduced risk of recurrence among women in the high-risk group by more than 70%, compared with no benefit from chemotherapy for those in the low-risk group, researchers said (Washington Post, 12/11). According to the Baltimore Sun, a third study of the test by researchers at Kaiser Permanente also was presented at the conference in San Antonio (Kohn, Baltimore Sun, 12/11).
"This test can identify 50% of patients who have an excellent prognosis and most likely don't need chemotherapy," lead researcher Soonmyung Paik of Genomic Health said, adding, "It appears that now we have a fairly objective means to tell patients, 'You do or do not need chemotherapy.' I think it's one of the most exciting findings in the last 10 years." Jeffrey Abrams of the National Cancer Institute said, "These study findings represent a major advance in our understanding of the role of genomics in cancer diagnosis and treatment, work that is critical to the national efforts to fight cancer." NCI's JoAnne Zujewski said, "This test has the potential to change medical practice by sparing thousands of women each year from the harmful short- and long-term side effects associated with chemotherapy."
Robert Blast of the University of Texas-M.D. Anderson Cancer Center, who co-wrote an editorial accompanying the study in NEJM, said, "This is an important advance toward individualizing patient care" (Washington Post, 12/11). He said the test "would probably make a difference in the treatment of tens of thousands of women." However, he added that the test is still a "work in progress" that requires more study before it can be used routinely (New York Times, 12/11).
Steven Shak, chief medical officer at Genomic Health, said, "OncotypeDX is like a molecular microscope. No longer are the inner workings of the cancer cell invisible." Shak said the company is working with insurance companies to determine whether they would cover the test (Washington Post, 12/11). The NEJM study is available online. Note: You need Adobe Acrobat Reader to view the study.