Researchers at Thomas Jefferson University in Philadelphia; Yale University in New Haven, Conn.; and Myriad Genetics in Salt Lake City compared 52 lumpectomy patients who later suffered cancer recurrences with 52 patients who did not.
Eight of the women whose cancer returned, or 15 percent, had inherited mutations in BRCA1 or BRCA2, the so-called breast-cancer genes. By comparison, in the group that suffered no recurrences, only one woman had inherited such a mutation.
Six of the eight hereditary breast-cancer patients who suffered recurrences were under age 43, suggesting that the earlier an inherited mutation causes cancer, the more likely it is to keep causing cancer.
The researchers found that women with genetic mutations took an average of eight years to relapse, compared with an average of five years for women without the defective genes. Lab tests on the tumors showed why: Women with mutations developed completely new breast cancers, while women without mutations either developed new cancers or grew back their original cancers, which had not been completely wiped out.
The researchers estimated that the eight women with mutations who relapsed had a 60 percent chance of developing cancer in their healthy breasts. The younger women in this group had a 40 percent chance of developing new cancer in the already-treated breast.
"Our data suggest that breast-conserving therapy may not be the most optimal treatment for breast-cancer patients with BRCA1 or BRCA2 mutations," said Bruce Turner, a Jefferson radiation oncologist and lead author of the study.
For some women with mutations, removing the healthy breast along with the cancerous one may be prudent, Turner said.
Of the 170,000 women in whom breast cancer is diagnosed annually in the United States, an estimated 15,000 have BRCA1 or BRCA2 mutations.
While the new study should help women and their doctors weigh treatment options, more research is needed before a blanket recommendation can be made, Turner said. Mastectomy dramatically reduces, but still does not eliminate, the risk of breast cancer because malignant cells can grow in the remaining chest wall tissue.
"It makes sense that by removing 90 to 95 percent of the breast-cancer cells by mastectomy, the future risk of breast cancer is significantly reduced," Turner said. "But more definitive data is needed before we can justify this recommendation."
In recent years, surgeons have vastly improved techniques for reconstructing breasts after mastectomy, "but it is still a large operation and a huge psychological issue," Turner said.
Turner said that hereditary cancer patients who undergo breast-conserving therapy should be told they are at high risk of recurrence, and be monitored with frequent breast exams and mammograms.
