The women who received the targeted therapy had higher levels of breast cancer recurrence -- 4.4 percent, versus 0.4 percent in the comparison group that underwent conventional therapy.
Despite this, overall five-year survival rates did not differ significantly between the two groups.
Baum said researchers next will look at whether providing a "boost" of radiation therapy during surgery will provide benefits to those women who will still need to undergo weeks of conventional therapy. "We think the results will be significantly better," he said.
U.S. oncologist Bernik predicts that radiation therapy during surgery will become more common, but that there are many kinks left to work out.
"This is the beginning of a new trend," Bernik said. "We have a lot of work to do to get to a point where this will be perfected."
For more information on breast cancer, visit the U.S. National Library of Medicine.
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