USPSTF Mammography Recommendations: Seeing Through the Screen
AbstraCt & Commentary
By Jeffrey T. Jensen, MD, MPH, Editor, Leon Speroff Professor of Obstetrics and Gynecology, Vice Chair for Research, Oregon Health and Science University, Portland, is Editor for OB/GYN Clinical Alert.
Synopsis: U.S. Preventive Services Task Force (USPSTF) issued a revised statement recommending against routine screening mammograms in women 40-49 years of age and against teaching self-breast exam skills.
Source: Screening for breast cancer: U.S. Preventive Services Task Force Recommendation Statement. Ann Intern Med 2009;151:716-726.
Based on results of two systematic evidence reviews, the USPSTF issued a revised statement regarding recommendations for breast cancer screening. The USPSTF recommends against routine screening mammography in women age 40-49 years, concluding that the risk of harm attributable to screening exceeds the potential benefit for low-risk women. Mammography for women age 50-74 years is recommended, but only every 2 years, and the USPSTF concluded that the evidence of additional benefits and harms of screening mammography in women 75 years or older was inconclusive. The Task Force found the evidence insufficient to recommend clinical breast examination in women age 40 years and older that undergo mammography, and determined that teaching breast self-examination (SBE) was harmful.
Commentary
The Nov. 17, 2009, release of the USPSTF revised recommendations on breast cancer screening made front page news, and left women's health professional groups and patient advocacy groups stunned. The most obvious departure from the group's last recommendations issued in 2002 was to advise against routine mammograms for women younger than age 50. Considering the massive efforts made to teach self-breast exam and encourage mammogram screening of women older than age 40, the recommendations were as surprising as those from the Women's Health Initiative (WHI) study. Like the WHI, the recommendations are based on the concept of balancing risk and benefit. Unlike the WHI, which presented new data from a large scale randomized controlled trial, the recommendations of the USPSTF represent a consensus report based upon a systematic review of the literature that sought to balance the potential benefits of screening mammography with risk and harm. The data showing that screening women younger than age 50 with mammograms, or of performing SBE at any age, was much more likely to result in additional testing and biopsy for benign disease than breast cancer led to the conclusion that women were more likely to be harmed than helped by screening. Interpretation of this information for patients requires a discussion of the consequences of under-diagnosis (death due to progression of a potentially treatable early cancer) and over-diagnosis (emotional, financial, and physical costs due to additional diagnostic procedures for benign breast changes or cancers that would never progress). Most of my patients accept the burden of screening to avoid this serious disease.
The absolute incidence rate of breast cancer climbs with age, rising from 58.8/100,000 in women age 35-39 years to 115.9/100,000 in women age 40-45 years, and 215.6/100,000 at age 50-55 years. To be effective, screening programs need to be targeted to a disease that is serious and prevalent, and the test must detect the presence of disease at an early stage that renders it treatable. Breast cancer is undeniably a serious and prevalent condition, and 95% of cases and 97% of deaths occur in women age 40 and older.1 More than 10% of all breast cancer deaths occur in women in their 40s.2
An ideal screening test would capture all with disease but exclude all that are well. In practice, the price of increasing sensitivity (detecting all true-positives) is lack of specificity (more false-positives). The predictive power of a positive (or negative) test is influenced by the underlying prevalence of disease; as disease prevalence increases so does the predictive power of a positive (or negative) test. Since about 10% of mammograms require additional evaluation, a large number of biopsies must be done to detect a single case of cancer. While this involves costs to the health care system and stress and anxiety to the affected individual, the overall benefit of mammography is worthwhile, and compares favorably to the cost and benefits of Pap smear screening for cervical cancer. Fine needle aspiration can reduce the need for open biopsy.3 Ultrasound,4 digital mammography,5 and MRI6 increase the sensitivity of detection, but greatly increase the number of false-positive screens. Therefore, combination screening is only recommended for very high-risk women (defined as a combination of factors that produces a 3-fold increase in risk), especially those women with dense breasts.
Do women in their 40s benefit enough from mammography to justify screening? The American Breast Cancer Detection Demonstration Project demonstrated that screening was just as effective for women in their 40s as in women older than age 50.7 Meta-analyses of randomized clinical trials concluded that in women age 40-49 offered mammography screening, there was about a 20% reduction in breast cancer mortality.8-10 Once detected by mammography, the stage of disease and survival expectations are the same comparing women age 40-49 with women older than age 50.11 However, breast cancer tends to grow faster in younger women, and cancers that are detected between screenings have lower survival rates (at all ages).12 Because the randomized clinical trials have screened younger women at 2-year or longer intervals, it is not surprising that screening has been less effective for these faster growing tumors. Rather than concluding (as the USPSTF did) that routine screening in the 40s is not effective, the basic biology of breast cancer would provide a sound argument that women age 40-49 should have annual screening mammography. A randomized trial in the United Kingdom of annual mammographic screening beginning at age 40 indicated a 24% reduction in breast cancer mortality in the screened women.13 As the proportion of women screened with mammography has increased, the death rate from breast cancer in the United States has declined 3.2% in women younger than age 50 compared with only 2% in women older than age 50.2 This decline in breast cancer mortality has been attributed to both improvements in breast cancer treatment and early detection.
The USPSTF recommendation against both clinical and self-breast examinations stems from the large number of follow-up imaging procedures and biopsies that occur in response to palpated masses. As discussed above, since the prevalence of cancer is low in young low-risk women, the chance of a breast cancer diagnosis is low with a biopsy for a palpable mass. However, the recommendations against breast self-exam come from randomized studies from Russia and China in women not receiving mammography that showed an increase in breast cancer detection with the introduction of SBE, but no difference in overall mortality. I find it hard to draw conclusions from these studies about the role of SBE in our population.14 While I agree that clinical breast exam is unlikely to provide the same level of benefit in mortality reduction as mammography (palpated lesions are more likely to have metastasized), SBE in women younger than age 40 represents the only strategy to pick up fast growing tumors.
The consensus panel recommendations are based in part upon a model of screening strategies performed by Mandelblatt et al and reported in the same issue of the Annals of Internal Medicine.15 Summary information from this publication (see Table) provides data that you can use to discuss these findings with patients considering screening. For example, annual mammograms starting at age 40 instead of age 50 and continued to age 69 will prevent 1 additional cancer death (8.3 vs 7.3) for every 1000 women screened at the expense of 63 unnecessary biopsies. You and she can decide if 10 additional years of mammogram screening and a 6% chance of getting a biopsy are worth the 0.1% chance of avoiding cancer mortality. There will be 70 fewer biopsies in 1000 women age 40-69 that get mammograms every other year compared to annually, but 2 additional women will die from breast cancer. In contrast, continuing annual mammograms until age 84 (compared to stopping screening at 74) will prevent 3 additional breast cancer deaths at the expense of only 22 unnecessary biopsies.15
The American Cancer Society and American College of Obstetricians and Gynecologists (ACOG) have not changed their recommendations for breast cancer screening in response to the USPSTF report. ACOG maintains its current advice that women in their 40s continue mammography screening every 1-2 years and women age 50 or older continue annual screening. In my practice, we recommend that women begin SBE monthly in the follicular phase (right after menstruation) and have annual clinical breast examination starting by age 35. Women with a first-degree relative with premenopausal breast cancer should begin annual mammography 5 years before the age of the relative when diagnosed. All other women should receive annual mammograms starting at age 40. Since the prevalence of breast cancer increases with age, the decision to stop routine mammogram screening should be based upon factors that include general health and life expectancy. Ultrasound should be added to screening for women with dense breasts, particularly those on HRT. Depending on local availability, MRI should be considered for evaluation of women at very high risk for breast cancer, especially younger women with dense breasts.
Are the risks and benefits of screening for breast cancer worth it? Ask your patients.
References
- American Cancer Society. Breast Cancer Facts & Figures 2009-2010. Atlanta, GA: American Cancer Society, Inc.; 2009.
- U.S. Cancer Statistics Working Group. United States Cancer Statistics: 1999-2005 Incidence and Mortality Web-based Report. Atlanta, GA: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention and National Cancer Institute; 2009. Available at: www.cdc.gov/uscs.
- Morris KT, et al. Usefulness of the triple test score for palpable breast masses. Arch Surg 2001;136:1008-1012.
- Berg WA, et al. Combined screening with ultrasound and mammography vs mammography alone in women at elevated risk of breast cancer. JAMA 2008;299:2151-2163.
- Pisano ED, et al. Diagnostic accuracy of digital versus film mammography: Exploratory analysis of selected population subgroups in DMIST. Radiology 2008;246;376-383.
- Warner E, et al. Systematic review: Using magnetic resonance imaging to screen women at high risk for breast cancer. Ann Intern Med 2008;148:671-679.
- Seidman H, et al. Survival experience in the Breast Cancer Detection Demonstration Project. CA Cancer J Clin 1987;37:258-290.
- Smart CR, et al. Benefit of mammography screening in women ages 40 to 49 years. Current evidence from randomized controlled trials. Cancer 1995;75:1619-1626.
- Berry DA. Benefits and risks of screening mammography for women in their forties: A statistical appraisal. J Natl Cancer Inst 1998;90:1431-1439.
- Humphrey LL, et al. Breast cancer screening: A summary of the evidence for the U.S. Preventive Services Task Force. Ann Intern Med 2002;137:347-360.
- Curpen BN, et al. The comparative value of mammographic screening for women 40-49 years old versus women 50-64 years old. AJR Am J Roentgenol 1995;164:1099-1103.
- Kerlikowske K, et al. Effect of age, breast density, and family history on the sensitivity of first screening mammography. JAMA 1996;276:33-38.
- Moss SM, et al. Effect of mammographic screening from age 40 years on breast cancer mortality at 10 years' follow-up: A randomised controlled trial. Lancet 2006;368:2053-2060.
- Nelson HD, et al. Systematic review: Comparative effectiveness of medications to reduce risk for primary breast cancer. Ann Intern Med 2009;151:703-715.
- Mandelblatt JS, et al. Effects of mammography screening under different screening schedules: Model estimates of potential benefits and harms. Ann Intern Med 2009;151:738-747.
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