Older women with an extended period of time between their last mammogram and the diagnosis of breast cancer are at an increased risk of dying from the disease, according to the results of a study presented at the American Association for Cancer Research (AACR) Annual Meeting 2013, held in Washington, D.C., April 6-10. The results indicate that there might be a need for continued screening among women over age 75.
A mammogram is an X-ray of the breast. Screening mammography is performed in a woman without breast symptoms in order to detect breast cancer at an early stage when it is most easily treated. Different groups of experts have reached different conclusions about when mammographic screening should begin and how often it should be performed. In 2009, the U.S. Preventive Services Task Force (USPSTF) issued guidelines recommending that routine screening of average-risk women begin at age 50 and be performed every two years. The guidelines indicate the lack of evidence for mammography for women 75 years or older based on the premise that disease would be indolent at advanced age; however, some data indicates that over 60% of breast cancers diagnosed between ages 70 to 79 were moderately or poorly differentiated.
To evaluate whether time between mammograms affected breast cancer mortality, researchers analyzed data from 8,663 women in the Women’s Health Initiative observational study or clinical trial who had been diagnosed with breast cancer during a 12.2-year follow-up. The analysis indicated that an interval of five years or more between last mammogram and breast cancer diagnosis was associated with advanced stage disease in 23 percent of women. In comparison, an interval of six months to a year was associated with advanced stage disease in 20 percent of women. The difference was considered statistically significant.
In an adjusted analysis, the researchers found that a longer interval between mammogram and diagnosis was associated with a significantly increased risk of breast cancer death among women age 75 or older at diagnosis. Women over age 75 who had an interval of five or more years between mammogram and diagnosis (or who had never had a mammogram) had three times the risk of dying from breast cancer compared with women who had an interval of six months to a year between mammogram and diagnosis. The same did not hold true for younger women.
The reasons for this trend are unclear, but the researchers note that the data may indicate a need for continued mammography screening in older women.
Simon MS, Wassertheil-Smoller S, Thompson CA, et al. Mammography interval and breast cancer mortality in the Women’s Health Initiative. Presented at the AACR Annual Meeting 2013, held in Washington, D.C., April 6-10. Abstract 157.