Dec. 13, 2007 (San Antonio) -- A test that characterizes breast tumors by their genetic fingerprint could spare tens of thousands of American women from the discomfort and misery of chemotherapy, researchers report.
Up to 40% of the 30,000 postmenopausal women diagnosed each year with estrogen-fueled breast cancers that have spread to the lymph nodes can safely skip chemotherapy, says Kathy Albain, MD, a breast cancer specialist at Loyola University Health System in Maywood, Ill.
The test, known as OncotypeDX, also identified a group of women at high risk of relapse who would definitely benefit from chemo, she tells WebMD.
Some doctors already use the test to predict whether women with cancer that hasn't spread to the lymph nodes are at low, medium, or high risk of recurrence.
The new study suggests that the test can also benefit women who typically face a harsher prognosis: Those whose disease has spread to the lymph nodes, Albain says.
The research was presented today at the annual San Antonio Breast Cancer Symposium.
40% of Women at Low Risk of Breast Cancer Relapse
The researchers analyzed tissue samples collected from 1,447 postmenopausal women with node-positive, estrogen-receptor positive breast cancer in the late 1980s and early 1990s. About one-fourth of breast cancers are classified as being node-positive, estrogen-receptor positive.
The tissue samples were analyzed for the activity of 21 genes involved in breast cancer risk. Depending on the activity of the genes, the women were assigned a recurrence score and classified as being at low, medium, or high risk of recurrence.
Results showed that 40% of women were at low risk of relapse, 28% were at intermediate risk, and 32% were at high risk of recurrence.
Low-Risk Women Don't Benefit
Then the researchers compared 361 women who got tamoxifen, an anti-estrogen drug, with 566 women who got chemotherapy followed by tamoxifen.
In those women with a low recurrence score, the risk of having a relapse over the next 10 years was about 40% regardless of whether chemotherapy was given.
"Many of these women can be told they don't need chemotherapy," Albain says.
But in women at high risk of relapse, there was a clear benefit: About 55% of those who got the one-two punch with chemotherapy and tamoxifen were relapse-free 10 years later, compared with only 43% of those who got tamoxifen alone.
"Sometimes we don't give chemo to older women, based on age alone. But the data shows we should be giving it to high-risk women regardless of age," Albain says.
What about women at intermediate risk? "Based on our data, we cannot rule out a benefit of chemotherapy, so it should still be given," she says.
"This is another example of how we can use newer technology to really identify women who need chemotherapy," says Dennis Slamon, MD, PhD, a breast cancer specialist at the University of California, Los Angeles.
"These were women we previously thought needed chemotherapy but turned out not to need it," he tells WebMD.