"If you had them, the [overall] survival was 94.6 percent; if not, 95.8. There's only a 1.2 percent difference between the two," Weaver said.
While the difference was significant from a statistical point of view, it was slight from a clinical point of view, he noted.
For women, Weaver said, the take-home message is not to be concerned about metastases being missed, provided the sentinel lymph node biopsy was done.
"Enough is enough as long as you find the macrometastases, the ones over 2 millimeters," he said.
As for the smaller spreads? "They are probably being treated by whatever cancer treatment is recommended [for the primary tumor]," he said, such as chemotherapy, endocrine therapy or radiation.
The new information "kind of solidifies an idea that we know," said Dr. Laura Kruper, an assistant professor of oncology and a breast cancer surgeon at the City of Hope Comprehensive Cancer Center in Duarte, Calif.
What the findings suggest, she said, is that the standard procedure followed by many -- do the sentinel lymph node biopsy alone if it's negative -- seems to be effective.
She added, however, that "we really do need to continue to follow these patients long-term" to see if the differences remain small.
To learn more about sentinel lymph node biopsy, visit the U.S. National Cancer Institute.
SOURCES: Donald L. Weaver, M.D., professor, pathology, University of Vermont College of Medicine and Vermont Cancer Center, Burlington, Vt.; Laura Kruper, M.D., assistant professor, oncology, and breast cancer surgeon, City of Hope Comprehensive Cancer Center,
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