The researchers focused primarily on whether the lack of hormone therapy increased the risk of death. But they also looked at cancer recurrences. "The identified low-risk group had fewer local and distant recurrences than patients not belonging to this group," Christiansen said.
"In Denmark, 85 percent of all patients with breast cancer have hormone-receptor positive tumors," Christiansen said. According to the American Cancer Society, two out of three breast cancers are these so-called ER-positive tumors.
The findings echo some previous studies, said Jennifer Griggs, an associate professor of internal medicine at the University of Michigan, in Ann Arbor. She co-authored an editorial on the study. The risk of death is already low in these patients with very small, hormone-positive beast cancer without lymph node involvement, she said.
The new study ''confirms what we know, but it leaves open a lot of questions as well," she said. "Not everyone needs systemic [hormone] therapy, but the question we are stuck with is, 'Who does?'"
Despite the findings, she writes that many women will want to take the hormone therapy to reduce their risk of recurrence, both in the breast with the original cancer and the opposite breast.
The greatest benefit of the therapy, she said, may be to prevent these recurrences. However, she said, some women have trouble tolerating the side effects of the hormone therapy. Those can include hot flashes and joint pain.
For those women who aren't sure if they want to go on the hormone therapy, which is typically given for five years, Griggs suggested they consider a trial of about three months. Then, depending on side effects, the woman can decide whether to stay on the treatment or not.
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