The critical question was whether treating the breast with a moderate dose of radiation would indeed lower the overall risk of a second cancer. "We know that there will be a balance between radiation killing premalignant cells and radiation producing premalignant cells, but it seemed that using the right radiation dose would put the balance strongly toward lowering the cancer risk," Dr. Brenner said.
The current study tested this hypothesis by performing PMI on transgenic mice that have a high risk of developing breast cancer, simulating the unaffected breast of a breast cancer survivor. Lead shields were positioned so that one side of each mouse was shielded from the radiation. As predicted, a moderate dose of radiation reduced the breast cancer risk in the treated side by a factor of about 3.
The researchers are now planning to test PMI in a clinical trial.
If PMI proves to be successful in patients, it could be used as an adjunct to tamoxifen or aromatase inhibitors for women with estrogen receptor-positive tumors and as a standalone therapy for those with estrogen-receptor negative tumors, who do not benefit from drug therapy. In either case, PMI could be performed concurrently with radiotherapy of the affected breast.
PMI could have a substantial clinical impact. At present, there are more than 2.6 million breast cancer survivors in the U.S., according to the American Cancer Society. "About 160,000 of these women are likely to develop cancer in their other breast," said Dr. Brenner. "If PMI does, in fact, reduce the incidence of cancer by three-fold, as suggested by our results, about 100,000 cases of breast cancer could be prevented."
"Whether PMI would work for women with BRACA1 or BRACA2 mutations, which greatly increase one's risk for breast and/or ovarian canc
|Contact: Karin Eskenazi|
Columbia University Medical Center