In November 2009, the United States Preventive Services Task Force (USPSTF) released new breast cancer screening guidelines. Unfortunately, this ill-timed release coincided with debate over healthcare reform leading to strong emotional reactions, misinformation, and controversy. Hopefully, with some time and distance, we can focus on the facts and expert opinions to better understand these guidelines for women at average-risk and also examine new data on the breast cancer screening options for women at high-risk.
First, it is important to address some of the basic questions that underlie this discussion:
What is screening?
Screening is an effort to findcancer before it causes noticeable symptoms with the hope that it will be found at an earlier stage when it may be easier to treat.
What are the available screening options for breast cancer?
• Film mammography: x-ray of the breast recorded on film
• Digital mammography: x-ray of the breast recorded electronically, allowing the use of software to enhance the image and aid in detection
• Ultrasound: bounces sound waves off of internal tissues and records the echoes to construct pictures
• Magnetic resonance imaging (MRI): uses radio waves, powerful magnetic fields, and a computer to construct detailed pictures of internal tissues
• Clinical breast exam (CBE): a physical exam of the breast performed by a healthcare provider to feel for lumps or concerning changes
• Breast self-exam (BSE): physical exam of the breast performed by an individual to feel for lumps or concerning changes in their breast tissue
What is the United States Preventive Services Task Force (USPSTF)?
The USPSTF is an independent panel of primary and preventive care experts established in 1984 to conduct systematic, unbiased reviews of the available scientific evidence regarding the effectiveness of various preventive medical services. They make recommendations based on a rigorous review of the data on the risks and benefits to patients. They are not a political group, do not consider the cost or coverage issues, and do not set federal policies or determine which services will be covered by federal programs. 1
What risks, benefits, and limitations are considered in making recommendations about breast cancer screening?
The benefit of a breast cancer screening method is often measured by its ability to reduce the risk of death from the disease. However, other measures of benefits are sometimes used including the number of cancers detected and the stage at which the cancers are detected.A number of potential risks and limitations can be considered, including:
•False negative results: The screening test results are normal even though a cancer is present, which may lead to false reassurance and cause a woman to delay seeking treatment for symptoms.
• False positive results: The screening test results are abnormal even though there is no cancer present, which can lead to anxiety, distress, additional screening tests, and unnecessary biopsies.
• Overdiagnosis: This is a more recently recognized and poorly understood risk but may prove to be one of the more serious risks. This means that a cancer is detected by screening that would never have caused symptoms or death and may have actually regressed without treatment. Since it is not possible to predict which cancers will result in symptoms and/or death and which will not, all cancers are treated with some combination of surgery, chemotherapy, radiation, or hormonal treatment. Therefore, some patients are unnecessarily exposed to the harms of these treatments and the emotional consequences of being diagnosed with cancer. 2
• Radiation exposure: Mammograms expose the breast tissue to low levels of radiation. High doses of radiation (e.g., chest wall radiation for treatment of lymphoma) have been shown to increase the risk of breast cancer. However, the amount of radiation exposure from mammograms is generally considered to be a low dose and thus safe.3
What breast cancer screening recommendations were made by the USPSTF and what do they really mean?
Keep in mind that these recommendations are intended for women at average risk for breast cancer.
The USPSTF:
Recommends biennial screening mammography for women aged 50-74 years. 4
This is based on data, which demonstrate that the benefits of mammography outweigh the risks in this age group. This extends previous screening recommendations from age 70 to age 74 and changes the recommended screening interval from every 1-2 years to every 2 years. This change was based on data that show a better balance of benefits and risks with screening every two years due to a significant reduction in the risks (false positive results and unnecessary biopsies) while maintaining most of the benefit (reduction in breast cancer mortality).5, 6
Recommends against routine screening mammography in women aged 40-49 years.
The decision to start regular, biennial screening mammography before the age of 50 should be an individual one and take patient context into account, including the patient's values regarding specific benefits and harms.4
This recommendation met with the most controversy. However, some of this was due to misinterpretation of the intent of the recommendation and unclearwording.1 It does not mean that mammograms are of no value to women in their forties or that no woman in her forties should have mammograms.> 1,6 In fact, mammograms do reduce the risk of death from breast cancer in women in their forties. 3,4,6 However, the risks associated with screening mammograms (false positive results) are higher at younger ages and thus the absolute benefit (comparing benefits to risks) is smaller. 1,3,4,6 The first sentence of this recommendation has now been removed to clarify the intent, which is that screening in this age group should not be automatic but instead involve an individual, informed decision by a woman and her healthcare provider based on a weighing of her personal risks, benefits, and values. 1, 4
Recommends against teaching breast self-examination. 4
The available data about BSE, although somewhat limited, show an association with an increase in unnecessary biopsies and no reduction in breast cancer mortality 3 This recommendation is in agreement with previous recommendations by other organizations. However, experts agree that women should still promptly bring any concerns about lumps or changes in their breasts to the attention of their physician.1,5
Concludes that there is insufficient evidence to assess the benefits and harms of several screening options including: screening mammography in women aged 75 and older, clinical breast exam (CBE), and digital mammography or MRI instead of film mammography.4
Is there any new data about breast cancer screening options for women at highrisk?
Although it did not receive the same attention as the USPSTF guidelines, another article published in November addressed breast cancer screening options for women at highrisk. This study compared the effectiveness of several additional breast cancer screening methods (digital mammograms, whole breast ultrasounds, and MRI) in 609 high-risk women who had a normal mammogram within 6 months of enrolling in the study. They concluded that MRI was more sensitive than mammograms and ultrasounds. Their data show that the addition of MRI to standard mammography screening is the most effective option for detecting additional cancers in high-risk women and thus supports the American Cancer Society recommendation of MRI screening for women with a >20-25% lifetime risk of breast cancer. They also conclude that digital mammograms are not a good replacement for MRI but may be an alternative to film mammograms in high-risk patients and that whole breast ultrasound should be reserved for patients who cannot undergo MRI. 7
In conclusion, women should discuss with their healthcare providers an individual breast cancer screening plan based on their breast cancer risk (considering their age, family history, genetic test results, and other risk factors) the risks, benefits, and limitations of the available options, and their preferences and values.
References:
1. Woolf SH. JAMA 2010; 303(2):162-163.2. Woloshin S and Schwartz LM. JAMA 2010; 303(2): 164-165.
3. Nelson HD et al. Annals of Internal Medicine. 2009; 151(10): 727-737.
4. US Preventive Services Task Force. Annals of Internal Medicine. 2009; 151(10): 716-726.
5. NCI Cancer Bulletin 2009; 6(22).
6. Partridge AH and Winer EP. New England Journal of Medicine 2009; 361(26): 2499-2501.
7. Weinstein SP et al. Journal of Clinical Oncology 2009; 27(36):6124-6128.