In 1990, the U.S. National Institutes of Health issued a consensus statement that breast-conserving surgery with radiation was equivalent to mastectomy, changing the practice of treating early breast cancer only with mastectomy.
Exactly why the preventive removal of the healthy breast is becoming more common isn't clear, Habermann said. "I think more women are hearing about it," she speculated.
More women may also be getting tested for the so-called breast cancer susceptibility genes, BRCA1 and BRCA2, and may choose to have the preventive mastectomy if they are positive for those, she added.
In other cases, exactly why a woman may opt for mastectomy even when her surgeon tells her the less-aggressive approach would be effective is not known, Habermann said. "But when you bring in anxiety to the equation, it may be the best choice for that woman," she noted.
And, she added, it's possible that mastectomy rates will increase again, despite the new findings.
The results do raise important questions, said Dr. Leonard Lichtenfeld, deputy chief medical officer for the American Cancer Society.
"Why would 26.4 percent of women with a tumor below 1 centimeter [as Habermann found] get a mastectomy?" he asked. "How much do we really know about what drives [decisions]?"
He points to the careful studies looking at lumpectomies. "We came up with a proven alternative," he said. "Why are some women voting with their feet and getting mastectomy in such a large percentage of cases?"
While SEER is an excellent database, he added, sometimes the patterns of care at leading cancer institutions, where some of the previous studies found a rise in mastectomy rates, eventually show up nationwide, he said.
Among other possibilities, he said, the increased use of MRI may be persuading more women or
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