Mammography Screening Guidelines

Excluding nonmelanoma skin cancers, breast cancer is the most common cancer in US women, and it is the second leading cause of cancer death in women in the United States, exceeded only by lung cancer.^[1,2] Early detection remains the primary defense in preventing breast cancer. It is essential for clinicians to not only review the most recent screening guidelines and recommendations but also be able to identify similarities and differences between the various mammography screening guidelines among medical organizations.

The goal of this slideshow is to assist medical professionals and patients in making appropriate decisions about screening for breast cancer in women.

Images courtesy of Gillian Newstead, MD, (magnetic resonance image [MRI]) and Medscape (sonogram).

Age and a positive family history of breast cancer are among the most widely recognized risk factors for breast cancer. A woman's lifetime risk is approximately doubled if her mother, sister, or daughter are affected; this risk is almost tripled in women who have two or more first-degree relatives with breast cancer.^[2]

Other breast cancer risk factors include female sex, white race/ethnicity, genetics, personal history of breast cancer and/or benign breast disease, and use of oral contraceptives or hormone replacement therapy.^[3,4]

Image data source: The American Cancer Society (ACS).^[2]

Screening and early detection have played significant roles in declining breast cancer deaths since the late 1980s, particularly in women younger than 50 years.^[2] Randomized controlled trials report a 15%-20% reduction in breast cancer deaths for women aged 40 to 74 years who are screened with mammography.^[5,6] Studies such as these highlight the importance of early detection.

Image information source: ACS.^[2]

The earliest sign of breast cancer is often an abnormality depicted on a mammogram, usually before it can be felt by the woman or her healthcare provider. In general, when breast cancer has grown to the point where physical signs and symptoms appear, the patient feels a breast lump that is usually painless. Survival rates are greatest when the breast cancer is detected in the early stages (shown).

Image data source: ACS.^[7]

Mammography is the preferred imaging examination for breast cancer.^[6] Ultrasonography, MRI, and nuclear medicine studies (eg, positron emission mammography [PEM], technetium-99m [^99mTc] mammoscintigraphy) are commonly used for adjuvant purposes and for follow-up evaluation when abnormalities are detected during mammography. These imaging modalities are also useful in younger patients with increased breast density whose mammograms may mask small masses/tumors.^[8]

There are slight variations in the mammography screening guidelines by various medical organizations. The ACS and American College of Radiology (ACR) recommendations are typically followed by radiologists and breast surgeons. The US Preventive Services Task Force (USPSTF) recommendations are typically followed by primary care physicians.

The ACS recommends that women aged 40 years and older should have annual mammograms, citing evidence of substantial benefit for women in their 40s, and clinicians should discuss the benefits and limitations associated with these yearly studies.^[9] Moreover, regardless of a woman's age and barring any serious comorbid conditions, mammograms should be continued.

Clinical breast examinations (CBE) are recommended in conjunction with mammography; these provide opportunities for women and their clinicians to discuss any breast changes, early detection testing, and potential predisposing risk factors for breast cancer.^[9] For women who use a step-by-step approach to breast self-examination (BSE), clinicians should review the woman's BSE technique during their physical examination, as well as discuss the benefits and limitations of BSE.^[9]

Image information source: ACS.^[9]

Despite the increased sensitivity of MRI, it should be used in addition to, not replace, screening mammography—mammography can detect some masses that are not revealed on MRI.^[9] The age at which high-risk patients should begin screening should be discussed between patients and their healthcare providers.

MRI uses no ionizing radiation and also has the following advantages^[10]:

• Capable of imaging (1) all possible planes, (2) the entire breast volume and chest wall, and (3) regional lymph nodes (although accurate staging remains problematic)
• Greater than 90% sensitivity for detecting invasive carcinoma; able to detect occult, multifocal, or residual malignancy
• Good spatial resolution, superb 3-D lesion mapping, and accurate size estimation for invasive carcinoma

Image information source: ACS.^[9]

The ACS indicates there is no evidence that MRI is an effective screening tool for average-risk women.^[9] In addition to there being no standard technique,^[10] MRI can have a higher false-positive rate, which can result in unnecessary tests and procedures and cause heightened patient anxiety.^[9]

Other disadvantages of MRI include the following^[10]:

• High equipment and examination costs and limited scanner availability
• Need for the injection of a contrast agent
• Poor throughput compared with that of ultrasonography or mammography
• Large number of images and long learning curve for interpretation
• Variable enhancement of in situ carcinoma; 5% incidence of slowly/poorly enhancing invasive carcinomas

Image information source: ACS.^[9]

The US Preventive Services Task Force (USPSTF) is a group of independent health experts appointed by the Agency for Healthcare Research and Quality (AHRQ) to develop consensus recommendations based on preventive and evidence-based medicine.^[11] In November 2009, the USPSTF issued updates to their breast cancer screening guidelines to recommend against routine mammography for women aged 40-49 years.^[12]

The USPSTF recommends biennial screening mammography for women aged 50 to 74 years.^[12] Biennial screening mammography before age 50 years should be individualized on the basis of the patient's risk factors and after discussion with her healthcare provider of the examination risks/benefits. The USPSTF concludes that there is insufficient evidence to assess the additional benefits/harms of screening mammography in women aged 75 years and older.^[12]

Image information source: USPSTF.^[12]

The USPSTF indicated that there should be no requirement for clinicians to teach women how to perform BSE.^[12] This recommendation was based on studies that found teaching BSE did not reduce breast cancer mortality but instead resulted in additional imaging studies and procedures, including biopsies.^[5,12]

An update to the 2009 USPSTF breast cancer screening recommendations is in progress.^[13]

Image information source: USPSTF.^[12]

Despite their differences in mammography screening frequency and age range (shown), the ACS^[9] and USPSTF^[12] guidelines agree that routine screening is recommended in asymptomatic women aged 50 to 75 years. Both guidelines also recommend thorough discussions between the woman and her healthcare provider about the benefits and risks of screening to reach an individual and informed decision.^[9,12]

As noted earlier, an update to the 2009 USPSTF breast cancer screening recommendations is in progress.^[13]

Despite the 2009 USPSTF recommendations, the American Congress of Obstetricians and Gynecologists (ACOG) (formerly the American College of Obstetricians and Gynecologists) recommends annual mammography screening in women beginning at age 40 years.^[14,15] Previously, ACOG recommended mammograms every 1-2 years starting at age 40 years and then annual mammograms beginning at age 50 years.

The BSE recommendation has shifted to include a new concept called "breast self-awareness" in women aged 20 years and older in which they have an "understanding [of] the normal appearance and feel of their breasts, but without a specific interval or systematic examination technique."^[14,15] Women should report any changes in their breasts to their healthcare providers.

Image information source: ACOG.^[14,15]

Clinicians should continually assess and determine a woman's breast cancer risk (eg, average, increased, high).^[16] Those that are established as being at increased or high risk can be offered "enhanced screening" options, such as CBE every 2 years, a yearly mammogram, a yearly MRI, and BSE guidance.^[15,16]

Image information source: ACOG.^[15]

The National Comprehensive Cancer Network (NCCN) guidelines highlight the importance of counseling patients about the potential risks/benefits of breast cancer screening.^[17] No upper age limit for screening currently exists.

The NCCN guidelines suggest that digital mammography can benefit young women and those with dense breasts, which are associated with an increased breast cancer risk. However, the NCCN concludes not enough evidence exists to support routine supplemental screening in women with dense breasts but without other risk factors. They note that "important outcomes are not yet established for supplemental screening; some states have passed legislation mandating patient notification of breast density."^[17]

Image information source: NCCN.^[17]

In addition to screening mammography, the NCCN guidelines recommend annual MRI screening for high-risk women on the evidence basis of (1) positive testing for BRCA mutation, (2) being an untested but first-degree relative of a BRCA carrier, and (3) having an increased lifetime risk (≥20%) for breast cancer (as determined by risk-factor prediction tools that based on family history).^[17]

On the basis of expert consensus opinion, in addition to screening mammography, the NCCN recommends annual MRI screening for high-risk women who have had thoracic irradiation between the age 10 and 30 years as well as in those with certain genetic syndromes (eg, Li-Fraumeni, Cowden, Bannayan-Riley-Ruvalcaba).^[17]

Stock images from Dreamstime.

Tomosynthesis mammography is a promising imaging modality for detecting malignant breast masses,^[17] particularly in women with dense breasts.^[18,19] This technique takes multiple images of the breast using a rotating scaffold and then combines them into a loop.^[18] The NCCN notes that two large studies demonstrated improved cancer detection and decreased call back rates when tomosynthesis was used in conjunction with digital mammography.^[17] However, the combined imaging modalities double the radiation dose, which must be taken into consideration.^[17,20] Investigation into tomosynthesis mammography is ongoing.^[17]

Image A shows a right breast digital mammogram with an area of focal increased density (arrowhead) without architectural distortion. Image B is a tomosynthesis mammogram revealing the smooth border of a mass (arrowheads) without malignant features in the same breast. The right image is a color sonogram in the same breast revealing a cysticlike lesion (C) with a hypervascular mural nodule (MN) that was ductal carcinoma in situ.

Images courtesy of Yang TL, Liang HL, Chou CP, Huang JS, Pan HB. Biomed Res Int. 2013;2013:597253. [Open access.] PMID: 23844366, PMCID: PMC3703369

It is essential for clinicians to consider all of the breast cancer screening guidelines from various medical organizations and to clearly communicate the information to women when making screening decisions on the basis of their risk level. Once the benefits and risks of different screening guidelines and imaging modalities have been discussed and weighed, an individual decision can be reached.