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Adapted from the NCI Cancer Bulletin, vol. 4/no. 28, October 23, 2007 (see the current issue ²).

Rates of surgical removal of both breasts as a preventive measure in women diagnosed with cancer in only one breast have more than doubled in the United States within a recent six-year period, according to a study published online October 22, 2007, in the Journal of Clinical Oncology (see the journal abstract ³). This trend has occurred even though in many cases the aggressive treatment may be unnecessary and other, less invasive preventive options are available, the scientists cautioned.

The annual incidence of contralateral breast cancer is about 0.5 percent to 0.75 percent and does not change with time. Some patients with cancer in a single breast (unilateral breast cancer) choose to have the other (contralateral) breast removed to prevent cancer in the opposite breast. The procedure is called a contralateral prophylactic mastectomy (CPM). In the first national study of trends in CPM use in the United States, researchers from the University of Minnesota analyzed data from NCI's Surveillance, Epidemiology and End Results (SEER) ⁴ database to review the treatment of patients with unilateral breast cancer diagnosed from 1998 through 2003. They determined the rate of CPM as a proportion of all surgically treated patients and as a proportion of all mastectomies.

The investigators identified 152,755 patients, of whom 4,969 chose CPM. The rate for CPM was 3.3 percent for all surgically treated patients and 7.7 percent for those undergoing mastectomy. The overall rate significantly increased from 1.8 percent in 1998 to 4.5 percent in 2003. Likewise, the CPM rate for patients undergoing mastectomy significantly increased from 4.2 percent in 1998 to 11.0 percent in 2003. These increased rates applied to all cancer stages and continued to the end of the study period.

CPM significantly reduces the risk of contralateral breast cancer, the scientists acknowledged, but the procedure is more aggressive and irreversible and "it is also unnecessary for preventing contralateral breast cancer in most patients." In addition, since the risk of systemic metastases from unilateral disease often exceeds the risk of contralateral breast cancer, most patients will not experience any survival benefit from CPM.

"Although breast cancer is now often diagnosed at earlier stages, we're seeing more women having CPM, even though there are very little data showing that this irreversible procedure improves overall survival," explained lead author Dr. Todd M. Tuttle. "We need to determine why this is occurring and use this information to help counsel women about the potential for less invasive options."

Dr. Larissa Korde, staff clinician with NCI's Division of Cancer Epidemiology and Genetics (DCEG) ⁵ noted of the study's findings, "Interestingly, during this same time period the rate of breast-conserving lumpectomies also increased, leading the authors to conclude that patients are either choosing less aggressive (lumpectomy) or more aggressive (CPM) surgical treatment rather than unilateral mastectomy."

Dr. Tuttle proposed several potential reasons for the increase in the rate of CPM. There is more public awareness of the genetics of breast cancer and more frequent testing for mutations in BRCA genes, which increase contralateral breast cancer risk (this study, though, did not examine patients' BRCA status). Less invasive mastectomy approaches and improved breast reconstruction techniques may also persuade more women to have both breasts removed at the same time, he suggested.

Dr. Korde pointed out the study also found that patients diagnosed at a young age and those diagnosed with lobular carcinoma were more likely to opt for CPM. "This is not surprising, since both these factors have been shown to be associated with an increased risk of contralateral breast cancer," she said. "It would have been very helpful to have some information on family history in this study, since women with a strong family history and particularly those with known BRCA1 and BRCA2 mutations have a very significant risk of contralateral breast cancer. However, this information is not available in the SEER database."

Patients with unilateral breast cancer have options that are "less extreme" than CPM, the researchers contended. Those include surveillance with clinical breast examination, mammography, and newer imaging modalities such as breast magnetic resonance imaging that may detect cancers at earlier stages.

Dr. Korde noted that research done in women who undergo genetic risk assessment suggests that those with more cancer-related distress are more likely to choose CPM. Additional research will be necessary to fully understand this decision making process.

Glossary Terms

Surgery to rebuild the shape of the breast after a mastectomy.

Having to do with the opposite side of the body.

The number of new cases of a disease diagnosed each year.

Cancer that begins in the lobules (the glands that make milk) of the breast. Lobular carcinoma in situ (LCIS) is a condition in which abnormal cells are found only in the lobules. When cancer has spread from the lobules to surrounding tissues, it is invasive lobular carcinoma. LCIS does not become invasive lobular carcinoma very often, but having LCIS in one breast increases the risk of developing invasive cancer in either breast.

Surgery to remove abnormal tissue or cancer from the breast and a small amount of normal tissue around it. It is a type of breast-sparing surgery.

A procedure in which radio waves and a powerful magnet linked to a computer is used to create detailed pictures of areas inside the body. These pictures can show the difference between normal and diseased tissue. Magnetic resonance imaging makes better images of organs and soft tissue than other scanning techniques, such as computed tomography (CT) or x-ray. Magnetic resonance imaging is especially useful for imaging the brain, the spine, the soft tissue of joints, and the inside of bones. Also called MRI, NMRI, and nuclear magnetic resonance imaging.

The use of film or a computer to create a picture of the breast.

The spread of cancer from one part of the body to another. A tumor formed by cells that have spread is called a “metastatic tumor” or a “metastasis.” The metastatic tumor contains cells that are like those in the original (primary) tumor. The plural form of metastasis is metastases (meh-TAS-tuh-SEEZ).

Surgery to reduce the risk of developing breast cancer by removing one or both breasts before disease develops. Also called preventive mastectomy.