A new gene test may spare thousands of women with a common type of breast tumor from unnecessary radiation, according to a study released Tuesday at the San Antonio Breast Cancer Symposium.
The test analyzes 12 genes from a woman's tumor; it helps predict which cases are likely to be aggressive, requiring both surgery and radiation, and which are likely to be slow-growing, needing surgery alone, says lead researcher Lawrence Solin, chairman of radiation oncology at Einstein Medical Center in Philadelphia. "This is a perfect example of how understanding the human genome can be translated into real life," he says.
The test, from Genomic Health, aims to help the more than 45,000 U.S. women a year diagnosed with ductal carcinoma in situ, or DCIS. Though some doctors consider the tumors very early breast cancers, others regard them as precancers. These tumors are confined to the milk ducts, but they have the potential to invade the rest of the breast.
Until now, however, doctors haven't had a good way to tell which cases of DCIS are the most likely to spread, Solin says. Patients often are treated as if they have a more advanced cancer, with lumpectomy and radiation, and sometimes years of hormonal therapies. In the case of DCIS, radiation reduces the risk of developing another tumor in the same breast, but doesn't improve survival, says Steve Shak, Genomic Health's chief medical officer.
And while radiation is generally safe, it can burn the skin and damage heart and lung tissue, Shak says. It's also time-consuming, requiring daily visits for five to seven weeks.
The study shows that about 75% of women fall into the "low-risk" category. After 10 years, only 5% developed an invasive cancer in the same breast. But 11% fell into the "high-risk" group; 19% of these developed invasive cancer within 10 years.
Women and doctors may want to use this information to guide treatment, Shak says. The DCIS test should be available by year's end. It isn't cheap -- current cost is $4,175 -- but radiation can cost more than $21,000.
"For women who really don't want radiation therapy or a mastectomy, this might well be a way to determine whether they 'should take the risk,'" says surgeon Susan Love of the Dr. Susan Love Research Foundation in Santa Monica, Calif.
Some cancer specialists aren't ready to change their practice, however. Eric Winer of Boston's Dana-Farber Cancer Institute, who wasn't involved in the new study, says he'd like to see additional studies before using the test to advise patients.
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