New Breast Cancer Screening Guidelines
Answers to 10 Questions?
In October, the American Cancer Society recommended women get fewer mammograms to screen for breast cancer. Many people were alarmed. Isn’t testing more often better? There are no simple answers, as the 10 common questions about breast cancer screening below illustrate.
- What are the new guidelines? The guidelines apply to women with average risk. From 45 to 54 years, a yearly mammogram is recommended. Women 55 years and older should get a mammogram every two years. Women are advised to stop screening if their life expectancy is less than 10 years.
- Why recommend younger women get more frequent mammograms? Younger women are less likely to develop breast cancer, but more likely to have rapidly growing breast cancers leading to death. That is the reason for screening younger women annually.
- When is the average women’s life expectancy less than 10 years? Approximately age 80. Most 75-year-old women live longer than 10 years. Few women live longer than 10 years after age 85.
- What are the criteria for recommending a cancer screening test like mammography? An ideal screening test would detect 100 percent of cancers at an early curable stage at low cost and never falsely label anyone with cancer.
- How close is mammography to this ideal? Far from ideal. Screening mammograms miss about 1 in 5 breast cancers. One common outcome of breast cancer screening is a “false positive test” that indicates possible cancer when none exists. Over a 10-year period of annual screening, 61 percent of women will have at least one false positive test. One advantage to testing every other year is reducing the risk of a false positive tests to 42 percent.
- How much does mammography reduce your risk of dying from breast cancer? All breast cancers detected are not curable. Typical estimates are 20-40 percent reduction in deaths from breast cancer with regular mammograms.
- What are the risks of mammography? The primary risk is a false positive test leading to additional testing. A false positive test commonly leads to extra imaging by mammography or ultrasound testing. Over 10 years, this leads to a biopsy for 7 percent of women. Testing every other year reduces this percentage to 4.8.
- How cost effective is mammography? One standard cost effectiveness measure is called QALY. QALY stands for Quality Adjusted Life Year. This measure is a combination of the number of additional years of life and a measure of their quality. The quality of life is measured by asking people how they would value a year of life in less than perfect health (i.e. unable to walk) compared with a year of life in perfect health. For example, screen with mammograms every other year from age 40 to 79 is estimated to cost $35,500 per QALY saved compared with no screening. Yearly screening starting at age 35 would cost $680,000 per added QALY.
- What about clinician breast examination and self-breast examination? There are no studies showing that self-breast examination improves outcome. Clinician breast examination detects 2 percent to 6 percent additional cancers compared with mammography, but no studies show this improves outcomes.
- What is your assessment of the new guidelines? The American Cancer Society did a careful job of weighing all of the evidence and developing reasonable recommendations. They are not perfect because we are currently unable to detect and prevent all breast cancers. The decreased number of false positive mammograms leading to biopsies is also positive. Another good point is the recommendations take personal preference into account. For example, the guideline recommends women have the opportunity to start annual screening at age 40 if they desire.
- Oeffinger KC, Fontham ET, Etzioni R, Herzig A, Michaelson JS, Shih YC, Walter LC, Church TR, Flowers CR, LaMonte S, Wolf AM, DeSantis C, Lortet-Tieulent J, Andrews K, Manassaram-Baptiste D, Saslow D, Smith RA, Brawley OW, Wender R: Breast Cancer Screening for Women at Average Risk: 2015 Guideline Update From the American Cancer Society. JAMA. 2015 Oct 20;314(15):1599-614
- Ahern CH, Shen Y: Cost-effectiveness analysis of mammography and clinical breast examination strategies: a comparison with current guidelines. Cancer Epidemiol Biomarkers Prev. 2009 Mar;18(3):718-25