BREAST CANCER SCREENING

The three most common modalities for breast cancer screening are mammogram, clinical breast examination, and breast self-examination. The goal of these screening examinations is to detect occult breast cancer at an early stage—before it is clinically evident—and thereby increase the probability of cure. A screening mammogram is an X-ray examination of the breast. The breast tissue is compressed, so that two views of the breast can be taken: a mediolateral (MLO) view and a craniocaudal (CC) view. If abnormalities are seen, then further images of the abnormality are taken, called magnification, or spot compression, views.

Mammogram screening is ideally performed in conjunction with a physical examination of the breast. These two examinations are complementary to one another—mammographic screening is able to detect some cancers that are not palpable, while some cancers are palpable, but not detectable on mammogram. Therefore, and of inestimable importance, a palpable abnormality needs to be evaluated further, even if the mammogram is normal.

Physical examination of the breast is performed in both the upright and supine positions. The patient is disrobed from the waist up for a complete examination. The breasts are inspected in the upright position with the arms relaxed, with the arms raised, and with the pectoral muscles contracted. The clinician is looking for differences in the breast size, alteration in the breast shape, or areas of skin retraction. The skin of the breast and the nipples are inspected. The regional lymph nodes are examined, including the axillary and supraclavicular lymph nodes. The breasts are subsequently palpated in the upright position and in the supine position, with the ipsilateral arm raised above the head. If a dominant mass is palpated, then further evaluation by a physician is warranted.

The first randomized controlled trial demonstrating the benefit of the screening mammogram and clinical breast exam in decreasing mortality was performed in 1963 by the Health Insurance Plan breast screening project. Sixty-two thousand women were randomized to either the intervention group, consisting of screening mammogram and clinical exam, or to a control group. At ten years of follow-up, the intervention group had a 30 percent reduction in breast cancer mortality.

Subsequent randomized trials of the screening mammogram also demonstrated a benefit to screening mammography. A meta-analysis of mammogram screening trials (9 randomized controlled trials and 4 case-control studies) was published in 1995. Data from the randomized controlled trials demonstrated that women between 40 to 74 years of age who underwent screening mammography had a relative risk of breast cancer of 0.79 (95% CI [confidence interval] 0.71–0.87) in comparison to unscreened patients. Women aged 50 to 74 (relative risk 0.77; 95% CI 0.69–0.87) benefited from screening mammogram more than women aged 40 to 49 (relative risk 0.92; 95% CI 0.75–1.13). The relative risk decreased to 0.83 (CI 0.65–1.06) after 10 to 12 years of follow-up. Based on these studies, screening mammography has been shown to decrease breast cancer mortality by approximately 30 percent.

The breast self-examination is a monthly examination of the breast performed by the patient. The goal of this examination is for the patient to notice any changes in her breasts that should subsequently be brought to the attention of a physician for further evaluation. It is estimated that patients discover approximately 65 percent of palpable breast abnormalities. For premenopausal women, the best time to perform the examination is one week after the start of menstruation. Postmenopausal women can perform the examination during any part of the month.

In performing the breast self-examination, the patient inspects her breasts in front of a mirror, with arms at her side and then with arms raised above her head. The nipples are gently squeezed to evaluate for discharge. The patient subsequently lies down and places the right arm above her head. The left hand is used to palpate the right breast. The breasts are examined in a circular motion with the fingers flat. All of the breast tissue and the axilla should be palpated. The opposite breast should be examined in a similar manner. The breasts should subsequently be examined in the shower. With one arm raised above the breast, the contralateral (opposite) hand is used to palpate the breast. The breasts are examined in a circular motion with the fingers flat. The patient is looking for breast lumps, changes in the breast shape, size, or contour, or for skin changes, puckering, or dimpling. Any of these abnormalities would warrant further evaluation by a physician.

The efficacy of breast self-examination in reducing mortality from breast cancer has not been established. Despite this, the exam is easily performed and of low cost. It should therefore be recommended to all women in the absence of better alternatives.

Clifford Hudis

Arti Hurria

(see also: Breast Cancer; Breast Self-Examination; Clinical Breast Examination; Mammography; Tamoxifen )

Bibliography

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Thomas, D. B.; Gao, D. L.; Self, S. G. et al. (1997). "Randomized Trial of Breast Examination in Shangai: Methodology and Preliminary Results." Journal of the National Cancer Institute 89:335–365.