Frequent Screening Mammos Detect Cancer Before Lymph Node Involvement

CHICAGO - Women whose breast cancer was detected by frequent screening mammograms had significantly lower rates of lymph node positivity than did those who had less frequent screenings, according to a study presented today at RSNA 2013.

Current screening recommendations from the United States Preventive Services Task Force (USPSTF), announced in 2009, say that women between 50 and 74 should be screened every two years, rather than annually. This runs contrary to RSNA and American Cancer Society guidelines, which encourage annual screening for women 40 and older.

Researchers from Northwestern University Feinberg School of Medicine in Chicago, Ill., undertook a retrospective study to assess what impact the new guidelines may have on women who were diagnosed with breast cancer by screening and whether the timing affected the number of patients who were found to have lymph node involvement. Treatment of breast cancer that has metastasized to the lymph nodes usually requires a broader approach of both local and systemic therapies.

A total of 332 women with breast cancer, identified by screening mammography between 2007 and 2010, were divided into one of three groups: those who had less than 1.5 years between screenings (207 women), those who went 1.5 to three years between screenings (73 women) and those who went for longer than three years between screenings (52 women).

The researchers found that the women who went more frequently for screening had the lowest rate of lymph node involvement when they were diagnosed with breast cancer (8.7 percent), while 20.5 percent in the 1.5-to-three-year group and 15.4 percent in the over three-year interval group had lymph node positivity. 

"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," said Lilian Wang, MD, assistant professor of radiology at the medical school. “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."