SUMMARY: Breast cancer is the most common cancer among women in the US and about 1 in 8 women (12%) will develop invasive breast cancer during their lifetime. It is estimated that 252,710 new cases of invasive breast cancer and 63,410 new cases of non-invasive breast cancer will be diagnosed in women in 2017 and 40,610 women are expected to die from the disease. In the US, about 33 million screening mammograms are performed each year.
Currently, the major national health care organizations in the US have different recommendations for screening mammography which has led to some confusion and emotional counterarguments. These several different recommendations include 1) Annual screening at ages 40 to 84 years 2) Annual screening at ages 45 to 54 years and then biennially at ages 55 to 79 years 3) Biennial screening at ages 50 to 74 years.
To address this varied recommendations and help women make informed decisions regarding mammography screening, the authors used computer modeling (CISNET models) to assess the three major screening mammography recommendations, and estimate the number of breast cancer deaths that might be prevented with the different screening mammography schedules. Cancer Intervention and Surveillance Modeling Network (CISNET) is a consortium of NCI-sponsored investigators who use statistical modeling to improve understanding of cancer control interventions in prevention, screening and treatment, and their effects on population trends in incidence and mortality. CISNET has been cited by the International Society Pharmacoeconomics and Outcomes Research (ISPOR) Task Force on Good Modeling Practices for its role in establishing a forum that enables researchers to compare results and articulate reasons for discrepancies.
It was noted in this study that the mean mortality reduction in breast cancer-specific deaths was greatest with the recommendation of annual screening at ages 40 to 84 years (39.6%), which meant that 29,369 lives were saved from breast cancer, compared with the recommendation of screening annually at ages 45 to 54 years, then biennially at ages 55 to 79 years (30.8%), which meant that 22,829 were lives saved from breast cancer, and the recommendation of biennial screening at ages 50 to 74 years (23.2%) which meant that 17,153 lives were saved from breast cancer.
The study also took into consideration risks associated with screening, including callbacks for additional imaging following indeterminate or suspicious mammographic finding and in some cases, a breast biopsy, only to find out that the findings were benign. The authors commented that the average woman in her 40s getting annual screening can expect additional and unnecessary screening about once every 12 years and unnecessary breast biopsy recommendations once every 150 years. Other rare risks with screening mammography include breast cancer that could be missed and breast cancer caused by mammogram radiation.
It was concluded that based on the CISNET models, the greatest breast cancer-specific mortality reduction is achieved with annual screening of women starting at age 40 years. They added that this is the first study to compare the three most widely discussed recommendations for screening mammography, head to head. These findings will guide women and their Health Care Providers in deciding when to begin screening mammography and how often to get screened. Comparison of recommendations for screening mammography using CISNET models. Arleo EK, Hendrick E, Helvie MA, et al. CANCER; Published Online: August 21, 2017. http://doi.wiley.com/10.1002/cncr.30842