Compression of the breast is necessary to obtain good images, and patients should be forewarned that breast compression is uncomfortable. With good technique and well-maintained modern equipment, exposure to radiation can be limited. Full-field digital mammography (FFDM) has a 22% lower mean glandular radiation dose than film-screen mammography per acquired view. FFDM delivers 1.86 mGy average breast radiation dose per view compared to 2.37 mGy for film screen (22).
The indications for mammography are as follows: 1.
To screen, at regular intervals, women who are at high risk for developing breast cancer. About one-third of the abnormalities detected on screening mammography prove malignant when biopsy is performed (23).
2.
To evaluate a questionable or ill-defined breast mass or other suspicious change in the breast that is detected by clinical breast examination.
3.
To establish a baseline breast mammogram and reevaluate patients at yearly intervals to diagnose a potentially curable breast cancer before it has been diagnosed clinically.
4.
To search for occult breast cancer in a patient with metastatic disease in axillary nodes or elsewhere from an unknown primary origin.
5.
To screen for unsuspected cancer before cosmetic operations or biopsy of a mass.
6.
To monitor breast cancer patients who were treated with a breast-conserving surgery and radiation.
Screening programs to evaluate asymptomatic, healthy women combine physical examination with mammographic screening to identify breast abnormalities. During the past 30 years, there was an increase in the use of mammography, mammographic screening, and public awareness of breast health care. The cancer detection rate for screening mammography is 5 per 1,000 screening examinations (24). The cancer detection rate is 11-fold higher, at 55 per 1,000 examinations, when breast imaging is performed for a specific finding (i.e., diagnostic imaging) (24). Of seven randomized mammographic screening trials performed, five demonstrated a reduction in overall mortality from breast cancer screening programs (25–32). A study from the Rhode Island Cancer Registry indicates that the institution of population-based breast cancer screening programs can result in the reduction in the median tumor size at initial detection from 2.0 to 1.5 cm, which is associated with a 25% reduction in mortality (33). A study from the Norwegian breast-cancer screening program was associated with a reduction in the rate of death from breast cancer, but the screening itself accounted for only about a third of total reduction (30). Detecting breast cancer before it spreads to the axillary nodes greatly increases the chance of survival; about 85% of women with such cancer will survive at least 5 years (31,34). Because breast cancer presents first as local disease, screening mammography for breast cancer in asymptomatic women can detect small tumors and offer a better prognosis. These tumors had less opportunity to metastasize regionally or systemically; thus women have more options for treatment with reduced toxicity.
The American Cancer Society published an extensive review of the benefits, limitations, and potential harms of screening mammography (35). It addresses the role of physical examination, discusses screening in older and high-risk women, and reviews the role of newer technologies. A summary of the guidelines recommends that women of average risk for breast cancer begin mammographic screening at age 40. The rationale for beginning mammographic screening at age 40 is a 24% reduction in mortality in screened populations (28). For women in their 20s and 30s, a clinical breast examination is suggested at least every 3 years, and preferably annually, as part of a well-woman examination. For women older than age 40 years, annual clinical breast examination and mammography are recommended. For older women, recommendations for mammographic screening may be individualized based on the presence of any comorbidities. Chronologic age alone should not be considered a contraindication to mammographic screening as long as a woman is in reasonable health and would be a candidate for breast cancer surgery (35).