The researchers than analyzed tissue samples supplied by the women, looking for the expression of HER2 as well as the tumor's estrogen receptor status.
"Most guidelines say, if a tumor is node-positive, chemo is recommended," Hayes said.
In this study, they found that paclitaxel helped those women whose tumors are HER2-positive, regardless of whether they were estrogen-receptor positive or negative. In contrast, patients whose cancers were HER2-negative and estrogen-receptor positive did not benefit in this study from paclitaxel.
Over the follow up of about 10 years, adding paclitaxel for the treatment of HER2-positive tumors reduced the risk of recurrence by 41 percent.
About 60 percent of women with breast cancer will have HER2-negative and estrogen-receptor positive tumors, noted Winer, who is chief scientific adviser for Susan G. Komen for the Cure, a nonprofit advocacy group.
Hayes did offer one strong caveat: "We want to be cautious about this data," he said, adding that the findings need to be confirmed in other studies.
Winer cautioned that the study, "doesn't tell us what we should do when we approach the patient in clinic tomorrow. We don't want people to say no to chemo based on these results only."
In an editorial accompanying the study, Dr. Anne Moore from Weill Cornell Medical College, New York City, concluded that "the days of 'one size fits all' therapy for patients with breast cancer are coming to an end.''
For more on breast cancer treatment, head to the American Cancer Society.
SOURCES: Daniel F. Hayes, M.D., clinical director, breast oncology program, University of Michigan Comprehensive Cancer Center, and p
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