Researchers say they've identified a genetic indicator of the long-term risk of breast cancer recurrence.
They compared three gene signature methods of predicting the risk of recurrence in patients treated for estrogen-receptor (ER)-positive breast cancer. They found that only the breast cancer index (BCI) -- a "biomarker" based on the expression levels of seven tumor-specific genes -- accurately identifies patients who continues to be at risk for breast cancer recurrence after five years of treatment with either tamoxifen or anastrozole, a drug in the aromatase inhibitor class.
The other two methods examined in the study were the Oncotype Dx Recurrence Score, the current gold standard for guiding clinical decision making, and the ICH4 gene signature, which is used less frequently used.
All three methods were able to predict recurrence risk in the first five years, but only the breast cancer index was able to accurately assess long-term recurrence risk, the study found. The breast cancer index was able to clearly distinguish 60 percent of patients whose risk was quite low from 40 percent who continued to be at significant long-term risk, the researchers said.
The study was published online Sept. 12 in the journal Lancet Oncology.
"We have validated a unique 'fingerprint' in the primary tumor of breast cancer patients that can help identify a high or low risk of cancer recurrence," study co-author Dr. Paul Goss, director of the breast cancer research program at Massachusetts General Hospital Cancer Center, said in a hospital news release. "This should enable us to offer prolonged treatment to patients who remain at risk and, importantly, to avoid the costs and side effects of treatment in those at low risk."
More than half the instances of recurrence in ER-positive breast cancer occur after five years of therapy with tamoxifen or anastrozole, so these findings are highly relevant to clinical management, study leader Dr. Dennis Sgroi, of the MGH Cancer Center, said in the news release.
"Since the BCI identifies two distinct risk groups, it may provide a much-needed tool in determining those patients who need extended hormonal therapy and those who may be spared its well-known adverse side effects," he explained.