Ask any woman with breast cancer if she'll do all that it takes to prevent a recurrence, and chances are she'll say, "Of course!" Yet she probably wouldn't choose to have chemotherapy—and the hair loss, nausea, fatigue, and potentially serious medical complications that come with it—if told that it probably wouldn't do much to lower an already low risk of relapse. Turns out, a genetic test called Oncotype DX that predicts a woman's chances of recurrence is, indeed, affecting doctors' and patients' decisions when it comes to chemotherapy, according to a study published Monday in the Journal of Clinical Oncology. About one third of the time, oncologists in the study changed their treatment recommendations after seeing the test result and about one quarter of the patients chose not to have unnecessary chemotherapy.
The test, which looks at 21 genes involved in determining the risk of recurrence, is most useful for those with stage 1 or 2 tumors that are small, respond to estrogen, and haven't spread to the lymph nodes; those with these tumors who take an antiestrogen drug like tamoxifen (which is separate from chemotherapy) typically have a 15 percent chance of recurrence after 10 years. But some have a risk lower than that, while others have a risk that's greater. The Oncotype test—now routinely covered by Medicare and most insurance companies—analyzes various gene mutations and assigns a score that indicates low risk, medium risk, or high risk.
For example, a woman with a score of 14 has a 9 percent risk of recurrence in 10 years and is classified as low risk, explains study author Shelly Lo, an assistant professor of medicine at Loyola University Medical Center in Maywood, Ill. Oncologists usually agree that this woman wouldn't benefit much from chemotherapy and can skip the infusions, she adds. On the other hand, a high-risk score above 31, which translates into a recurrence risk higher than 15 percent in the next 10 years, would indicate a good candidate for chemo. "For women at medium risk," Lo says, "it's not clear whether the risks of chemotherapy outweigh its benefits." Six women out of the study's 89 participants fell into this category, with just one choosing to have chemotherapy.
Interestingly, nearly 1 in 4 oncologists in the study didn't routinely order the Oncotype test, so women with early-stage breast cancer should ask for it themselves before opting for or against chemotherapy. Those with estrogen-receptor-negative tumors, however, need chemotherapy regardless of the test result, says Lo, because they don't benefit from other adjuvant therapies like tamoxifen.
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