Although the 2009 U.S. Preventive Services Task Force suggested that women at normal risk for breast cancer should begin mammography screening starting at age 50, and get screened every other year, the consensus among leading organizations continues to be that women should begin annual mammograms at age 40.
“Approximately 15 percent of breast cancers occur between the ages of 40 and 50,” says Lawrence Bassett, M.D., section chief of the Iris Cantor Center for Breast Imaging. “Beginning at 40 gives us a good baseline to start with and helps us catch most cancers that occur when a woman is in her 40s.” Routine screening is important, Dr. Bassett says, because breast cancers that go untreated for a long time are more likely to metastasize to other parts of the body.
Mammography screening aims to find breast cancers before they are large enough to be detected in a clinical exam. “Early detection results in less severe treatment and a greater likelihood of surviving breast cancer,” says Anne Hoyt, M.D., medical director of the Santa Monica UCLA Women’s Imaging Center. “Many of the tumors found by screening are in an early stage and confined to the breast.”
Women at elevated risk of developing breast cancer should begin annual mammography screening sooner. If a woman’s risk is very high, she may also require screening with magnetic resonance imaging (MRI), Dr. Hoyt notes. For women considered to be at very high risk, including those known to carry mutations in the BRCA-1 and BRCA-2 genes or who have a strong family history of breast cancer, the recommendation may be to screen every six months, alternating between mammograms and MRIs.
Dr. Hoyt points out that women without known risk factors are still susceptible and should follow the screening guidelines. “Approximately 75 percent of breast cancers are diagnosed in women with no identifiable risk,” she says.
Mammography isn’t infallible, Dr. Bassett notes. In particular, dense breast tissue can mask a tumor. Digital breast tomosynthesis, also called 3D mammography, was recently approved by the U.S. Food and Drug Administration as an add-on to the conventional two-dimensional mammogram. Studies have shown that 3D mammography can reduce false positives (findings that are suspicious enough to require further testing but turn out to be benign) while improving the ability to detect cancers that would otherwise be hidden by overlapping tissue.
“There is no perfect screening method,” Dr. Bassett concludes, “but mammography is the best tool that we have, and it has been proven to reduce breast cancer mortality.”