Early Detection of Breast Cancer

Screening Programs
A number of mass screening programs consisting of physical and mammographic examination of the breasts of asymptomatic women have been conducted. Such programs frequently identify about 10 cancers per 1000 women older than age 50 years and about 2 cancers per 1000 women younger than age 50 years. About 80% of these women have negative axillary lymph nodes at the time of surgery, whereas only 50% of nonscreened women found in the course of usual medical practice have uninvolved axillary nodes. Detecting breast cancer before it has spread to the axillary nodes greatly increases the chance of survival, and about 85% of such women will survive at least 5 years.

Both physical examination and mammography are necessary for maximum yield in screening programs, since about 35-50% of early breast cancers can be discovered only by mammography and another 40% can be detected only by palpation. About one-third of the abnormalities detected on screening mammograms will be found to be malignant when biopsy is performed. The probability of cancer on a screening mammogram is directly related to the Breast Imaging and Reporting Data System (BIRADS) assessment, and workup should be performed based on this classification. Women 20-40 years of age should have a breast examination as part of routine medical care every 2-3 years. Women over age 40 years should have yearly breast examinations. The sensitivity of mammography varies from approximately 60% to 90%. This sensitivity depends on several factors, including patient age (breast density) and tumor size, location, and mammographic appearance. In young women with dense breasts, mammography is less sensitive than in older woman with fatty breasts, in whom mammography can detect at least 90% of malignancies. Smaller tumors, particularly those without calcifications, are more difficult to detect, especially in dense breasts. The lack of sensitivity and the low incidence of breast cancer in young women have led to questions concerning the value of mammography for screening in women 40-50 years of age. The specificity of mammography in women under 50 years varies from about 30% to 40% for nonpalpable mammographic abnormalities to 85% to 90% for clinically evident malignancies.

Doubt exists about the beneficial effect of screening, especially in women under age 50 years. Questions such as the potential harmful effects of x-rays in a large population of young women and the general value of early detection were raised and largely ignored as various groups supported screening between ages 40 and 50 years. Although the Health Insurance Plan Project study did show a beneficial effect of screening in such women, reducing breast cancer mortality 25% between 10 and 18 years after entry into the study, a Canadian trial demonstrated an unexplained shortening of survival from time of random assignment to death in the screening group. The small number of patients in this study experienced no beneficial effect, but the 95% confidence interval included a potential lifesaving effect as well as a potential harmful effect. A very large number of patients is necessary to show a beneficial effect of screening among patients aged 40-49 years, in whom the incidence of breast cancer is low. In addition, the problems of crossover of patients in the control group with women undergoing physician examination and nonscreening mammograms, problems with mammography quality, and problems in recruitment, randomization, and compliance make the interpretation of such trials difficult. The beneficial effect of screening in women aged 50-69 years is undisputed and has been confirmed by all clinical trials. The efficacy of screening in older women - those older than 70 years - is inconclusive and is difficult to determine because few women were screened.

More recent studies showing a beneficial effect of screening young women and the recommendation of a Swedish consensus panel led the National Cancer Institute (NCI) to reconsider its position on screening mammography for women in their 40s. Two Swedish trials that had shown a 13% decrease in breast cancer mortality (not statistically significant) now showed a statistical advantage for screening women in their 40s, and a meta-analysis similarly revealed a statistical survival advantage for screened women with longer follow-up. In March 1997, the National Cancer Advisory Board recommended that women in their 40s with average risk factors should have screening mammography every 1-2 years and that women at higher risk should seek medical advice on when to begin screening. The American Cancer Society then recommended screening every year for asymptomatic women starting at age 40 years. Studies continue to support the value of screening mammography.

Breast self-examination (BSE) has not been shown to improve survival. Despite this and despite possible increased biopsy rates, it is a useful technique since many patients do detect their own cancer, and women often feel more in control and proactive by using the procedure. Because of the absence of strong evidence supporting the value of BSE, the American Cancer Society no longer recommends monthly BSE beginning at age 20 years. The recommendation is that patients be made aware of the potential benefits, limitations, and harms (increased biopsies or false-positive results) associated with BSE. Women who chose to perform BSE should be advised regarding the proper technique. Premenopausal women should perform the examination 7-8 days after the menstrual period. The breasts should be inspected initially while standing before a mirror with the hands at the sides, overhead, and pressed firmly on the hips to contract the pectoralis muscles. Masses, asymmetry of breasts, and slight dimpling of the skin may become apparent as a result of these maneuvers. Next, in a supine position, each breast should be carefully palpated with the fingers of the opposite hand. Some women discover small breast lumps more readily when their skin is moist while bathing or showering. Physicians should instruct women in the technique of self-examination and advise them to report a mass or other abnormality.

Mammography is the most useful technique for the detection of early breast cancer. Film screen mammography delivers less than 0.4 cGy to the mid breast per view and has largely replaced the older xeromammographic technique, which delivers more radiation.

Mammography is the most reliable means of detecting breast cancer before a mass can be palpated. Slowly growing cancers can be identified by mammography at least 2 years before reaching a size detectable by palpation. Although full-field digital mammography provides an easier method to maintain and review mammograms, it has not been proven that it provides better images or increases detection rates more than film mammography. New computer-assisted detection (CAD) has not shown any increase in detection of cancers and is not routinely performed at centers with experienced mammographers.

Calcifications are the most easily recognized mammographic abnormality. The most common findings associated with carcinoma of the breast are clustered polymorphic microcalcifications. Such calcifications are usually at least five to eight in number, aggregated in one part of the breast and differing from each other in size and shape, often including branched or V- or Y-shaped configurations. There may be an associated mammographic mass density or, at times, only a mass density with no calcifications. Such a density usually has irregular or ill-defined borders and may lead to architectural distortion within the breast. A small mass or architectural distortion, particularly in a dense breast, may be subtle and difficult to detect.

Indications for mammography are as follows: (1) to screen at regular intervals women at high risk for developing breast cancer (see above); (2) to evaluate each breast when a diagnosis of potentially curable breast cancer has been made, and at yearly intervals thereafter; (3) to evaluate a questionable or ill-defined breast mass or other suspicious change in the breast; (4) to search for an occult breast cancer in a woman with metastatic disease in axillary nodes or elsewhere from an unknown primary; (5) to screen women prior to cosmetic operations or prior to biopsy of a mass, to examine for an unsuspected cancer; and (6) to follow those women with breast cancer who have been treated with breast-conserving surgery and radiation.

Patients with a dominant or suspicious mass must undergo biopsy despite mammographic findings. The mammogram should be obtained prior to biopsy so that other suspicious areas can be noted and the contralateral breast can be checked. Mammography is never a substitute for biopsy because it may not reveal clinical cancer in a very dense breast, as may be seen in young women with fibrocystic changes, and may not reveal medullary cancers.

Communication and documentation among the patient, the referring physician, and the interpreting physician are critical for high-quality screening and diagnostic mammography. The patient should be told about how she will receive timely results of her mammogram; that mammography does not “rule out” cancer; and that she may receive a correlative examination such as ultrasound at the mammography facility if referred for a suspicious lesion. She should also be aware of the technique and need for breast compression and that this may be uncomfortable. The mammography facility should be informed in writing of abnormal physical examination findings. It is strongly recommended in the Agency for Health Care Policy and Research (AHCPR) Clinical Practice Guidelines that all mammography reports be communicated with the patient as well as the health care provider in writing. Additional phone communication about any abnormal findings should take place between the interpreting and referring physicians. Magnetic resonance imaging (MRI) and ultrasound are currently being studied as screening tools for breast cancer. They may be useful modalities in women who are at high risk for breast cancer, but not for the general population. The sensitivity of MRI is much higher than mammography; however, the specificity is significantly lower and this results in multiple unnecessary biopsies. The increased sensitivity despite decreased specificity may be considered a reasonable trade-off for those at increased risk for developing breast cancer, but not for a normal-risk population. Additionally, positron emission tomography (PET) may play a role in imaging atypical lesions, but only after diagnostic mammography has been performed.

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Revision date: July 4, 2011
Last revised: by Tatiana Kuznetsova, D.M.D.