Dec. 7, 2011 -- A test that categorizes very early breast cancers by their genetic fingerprint can tell a woman the likelihood that cancer may come back if she does not have radiation, researchers say.
More than 45,000 women in the U.S. are diagnosed with this early form of breast cancer, called ductal carcinoma in situ (DCIS), each year. The tumors are confined to the milk ducts, meaning they have not invaded the rest of the breast.
The researchers’ hope is that the test, which looks at the activity of a dozen genes from such noninvasive breast cancers, will help women with DCIS avoid unnecessary radiation.
"Until now, we haven’t had a good way to predict which individual [noninvasive] tumors will recur," either as a new DCIS or, worse, as an invasive cancer, says researcher Lawrence Solin, MD, chairman of radiation oncology at Einstein Medical Center in Philadelphia.
Solin presented the findings here at the San Antonio Breast Cancer Symposium. Genomic Health, which makes the test and funded the research, hopes to launch it within a few weeks.
About half of women with DCIS will develop invasive cancer over the next few decades if nothing is done, according to Benjamin D. Smith, MD, of the University of Texas M.D. Anderson Cancer Center in Houston. Smith, who specializes in radiation treatment for women with breast cancer, was not involved with the work.
As a result, these women are usually treated as though they have more advanced cancers -- typically with lumpectomy, followed by radiation of the breast, and sometimes hormonal drugs, he tells WebMD.
Compared with surgery alone, radiation reduces the risk of recurrence by 50% to 60%, Smith says.
But radiation is not without side effects. It can cause skin inflammation and make you tired. And over the long term, it can damage heart and lung tissue.
All this points to a need for a test that can guide a discussion on whether radiation treatment can be safely skipped, Solin tells WebMD.
Test Predicts Breast Cancer Recurrence Risk
The new study involved 327 women with DCIS who had been treated with lumpectomy, but not radiation, as part of a previous clinical trial. Over the next decade, 26 developed invasive cancer in the same breast.
Using tumor tissue that had been frozen at the time the women were treated, the researchers used the new test to see if it could identify those at higher risk for an invasive cancer and those at lower risk. It did, Solin says.
About three-fourths of the women fell into a "low-risk" category, with only a 5% chance of having cancer come back over a 10-year period.
Eleven percent of the women were classified as "high-risk." Their odds of having a new invasive cancer over a decade: Nearly 20%.