Mammography Screening Intervals May Affect Breast Cancer Prognosis

In a study of screening mammography-detected breast tumors, patients who had more frequent screening mammography exams had a considerably lower rate of lymph node positivity as compared to women who had longer intervals between screening-mammography exams.

The study’s findings were presented December 3, 2013, at the annual meeting of the Radiological Society of North America (RSNA), held December 2013 in Chicago (IL, USA). In its earliest stages, breast cancer is confined to the breast and can be treated by surgically removing the cancer cells. Breast cancer cells may metastasize to the lymph nodes as the disease progresses and then to other areas of the body.

“On its pathway to other places in the body, the first place breast cancer typically drains into before metastasizing is the lymph nodes,” said Lilian Wang, MD, assistant professor of radiology at Northwestern University/Feinberg School of Medicine (Chicago, IL, USA). “When breast cancer has spread into the lymph nodes, the patient is often treated both locally and systemically, with either hormone therapy, chemotherapy, trastuzumab, or some combination of these therapies.”

Healthcare organizations, such as RSNA and the American Cancer Society (ACS), have recommended yearly screening with mammography for women beginning at age 40. However, in 2009, the United States Preventive Services Task Force (USPSTF) announced a controversial new recommendation for biennial screening for women between the ages of 50 and 74. “Our study looks at what would happen if the revised guidelines issued by USPSTF were followed by women,” Dr. Wang said.

Conducted at Northwestern Memorial Hospital (Chicago, IL, USA), the retrospective study, included 332 women with breast cancer identified by screening mammography between 2007 and 2010. The women were split into one of three groups, based on the length of time between their screening mammography exams: less than 1.5 years, 1.5 to three years, and more than three years. There were 207, 73, and 52 patients in each category, respectively.

The researchers determined, controlling for age, breast density, high-risk status, and a family history of breast cancer, that women in the less than 1.5-year interval group had the lowest lymph node positivity rate at 8.7%. The rate of lymph node involvement was substantially higher in the 1.5- to three-year and over three-year interval groups at 20.5% and 15.4%, respectively.

“Our study shows that screening mammography performed at an interval of less than 1.5 years reduces the rate of lymph node positivity, thereby improving patient prognosis,” Dr. Wang concluded. “We should be following the guidelines of the American Cancer Society and other organizations, recommending that women undergo annual screening mammography beginning at age 40.”

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Northwestern University/Feinberg School of Medicine