Advanced cancer risk similar with biennial vs. annual mammography in women aged 50 to 74

Abstract

A study comparing the benefits and harms of the frequency of screening mammography indicates that women aged 50 to 74 years who are screened every other year have a similar risk of advanced stage disease and a lower cumulative risk of falsepositive results than those who are screened annually. The study was led by Karla Kerlikowske, MD, of the University of California at San Francisco.1 She and her colleagues attempted to determine whether the benefits and harms of annual versus biennial screening mammography vary according to age, breast density, and postmenopausal hormone therapy (HT) use. The study was prompted by the 2009 recommendation by the US Preventive Services Task Force that women aged 50 years to 74 years receive biennial screening mammography versus the previous recommendation of every 1 to 2 years. Dr. Kerlikowske and her colleagues analyzed data from January 1994 to December 2008 from community mammography facilities that participate in the Breast Cancer Surveillance Consortium mammography registries. The data included information gathered from 11,474 women with breast cancer and 922,624 women without the disease. Researchers found that biennial screening mammography was not associated with an increased risk of advanced stage disease or large tumors regardless of a woman's breast density or HT use. However, researchers did find that women aged 40 to 49 years with extremely dense breasts had an increased risk of advanced stage cancer (odds ratio, 1.89) and large tumors (odds ratio, 2.39) with the use of biennial screening mammography compared with annual screening. The cumulative probability of a false-positive result also was high for women with extremely dense breasts who were either aged 40 years to 49 years or who used estrogen plus progestogen and underwent annual screening mammography. Those rates were 65.5% and 65.8%, respectively. Conversely, it was lower among women aged 50 to 74 years with scattered fibroglandular densities or fatty breasts who underwent biennial or triennial screening mammography. Researchers concluded that women aged 50 years to 74 years can undergo biennial rather than annual screening mammography, regardless of breast density or HT use, because the former does not increase the risk of advanced disease but substantially reduces the cumulative risk of false-positive results and biopsy recommendations. Meanwhile, women with extremely dense breasts who are aged 40 to 49 years should consider annual screening mammography to decrease the risk of advanced stage disease; however, they should be aware of the higher probability of false-positive results.