Overview
1. The lifetime risk (to age 85) of a woman developing breast cancer in 1940 was 5% or one in 20; the risk is now 12.6% or one in 8. In women 40 to 49 years of age, there is a one in 69 risk of developing breast cancer compared with a one in 38 risk among women in the 50 to 59 year age group.
2. Randomized, controlled trials have demonstrated reduced mortality rates (20% to 40%) from breast cancer among women invited to undergo screening mammography compared with control groups.
3. Although statistically significant benefits/reductions in breast cancer mortality are delayed 10 to 15 years among women 40 to 49 years of age at the time of screening, several of the screening trials have reported a benefit (23% to 44%) from screening women 40 to 49 years of age.
4. The benefit of mammography is related to early detection. Regardless of the histological grade of a tumor, a greater than 90%, ten-year survival rate has been reported in 40- to 74-year old women diagnosed with tumors that are 10 mm or smaller in size.
5. The effectiveness of any screening program will depend on screening frequency, compliance with screening recommendations and the quality of the screening test.
6. In establishing screening frequencies, breast cancer growth rates need to be considered. The sojourn time (average time for mammographically detectable, pre-clinical cancers to become clinically apparent) for all breast cancer types is shorter for pre-menopausal women compared with post-menopausal women, supporting annual screening in 40 to 49 year old women: 1.8 years in 40 to 49 year old women and 3.5 years in women 50 years of age or older.
Recommendations for breast cancer screening
The American Cancer Society recommends:
1. Breast physical examination by a health care provider every three years starting at age 20; annual clinical breast physical exam starting at age 40
2. Annual screening mammography starting at age 40
3. Women in high risk categories (first degree relative with breast cancer; personal history of breast cancer; prior biopsy with atypical ductal hyperplasia or lobular carcinoma in situ) may want to consider starting screening at age 30.
The New United States Preventive Services Task Force (USPSTF) guidelines recommend biennially screening mammography in women starting from age 50 to 74.
Reference material
1. U.S. Preventive Services Task Force: Screening for Breast Cancer Recommendation Statement November 2009. 2. Breast Cancer Screening for Women Ages 40-49. NIH Consensus Statement 1997; January 21-23; 15(1): In-press.
3. American Cancer Society, Workshop on Guidelines for Breast Cancer Detection, Chicago, March 7-9, 1997. Available http://www.cancer.org/mammog.html, October 7, 1997.
4. Salzmann P, Kerlikowske K, Phillips K. Cost-Effectiveness of Extending Screening Mammography Guidelines to Include Women 40 to 49 Years of Age. Annals of Internal Medicine 1997; 127: 955-965.
5. Ransohoff DF, Harris RP. Lessons from the Mammography Screening Controversy: Can We Improve the Debate? Annals of Internal Medicine 1997; 127: 1029-1034.
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