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Genetic test may predict breast cancer recurrence over 10 years

Breast cancer researchers are reporting a new test may predict which women will have their cancers come back over a 10-year period, about double the time of currently-used tests.

"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," Dr. Paul Goss, study co-author and director of the Breast Cancer Research Program at Massachusetts General Hospital Cancer Center in Boston, said in a statement.

Most breast cancer recurrences occur within the first three to five years following treatment, WebMD reports.

According to government figures, more than 232,000 women and 2,200 males are expected to be diagnosed with the disease this year.

Roughly 75 percent of all breast cancers are "estrogen-receptor positive," meaning they grow in response to the sex hormone estrogen. These cancers are often treated with five years of endocrine therapies that block estrogen, including the drug tamoxifen or drugs called aromatase inhibitors.

Most women won't experience breast cancer recurrence if treated early, but some may have the cancer return in the breast or elsewhere in the body. Tumor size, involvement of lymph nodes, a gene called HER2 and hormone receptors like estrogen and progesterone are all risk factors for recurrence, WebMD notes.

Massachusetts General Hospital researchers compared three current methods that predict recurrence risk in women with estrogen-receptor-positive breast cancers. The first method was the breast cancer index (BCI), which looks for biomarkers -- molecular signals in the body -- of seven tumor-specific genes. Another test examined was the Oncotype Dx Recurrence Score, an analyzer of 21 genes in tumor samples. The researchers also looked at a less-frequently used genetic test looking at the ICH4 gene, which is linked to breast cancer.

They used the tests to look at tumor samples from 665 patients, then compared their findings to actual medical records from the patients to see if breast cancer recurrence actually occurred within five and ten years.

All three methods accurately predicted recurrence risk within the first five years, but only the BCI method -- which was developed by MGH researchers and a company, bioTheranostics, Inc. -- predicted risk within 10 years. Notably, BCI could clearly distinguish 60 percent of patients who had very low risk for recurrence and 40 percent who were at significant long-term risk.

"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," said Goss.

The study was published Sept. 11 in Lancet Oncology.

Study leader Dr. Dennis Sgroi, a cancer researcher and pathologist at MGH, said since more than half of breast cancer occurrences occur within five years, his study's findings could help oncologists managing patients.

"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 said.

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