Breast Cancer Screening
A variety of tests are used for the diagnosis of breast cancer.
Screening mammography has made it possible to detect many breast cancers before they produce any signs or symptoms. While there is no doubt that mammography is important, recommendations regarding frequency and age at which women should begin receiving screening mammography differ slightly between different organizations and task forces.
The American Cancer Society (ACS) recommendations for breast cancer screening were changed in October 2015, and now are considered evidence-based guidelines based on extensive review of available studies. They are as follows:
- The Clinical Breast Exam (CBE) is no longer felt to be indicated in asymptomatic, average-risk women (women with no past history of breast cancer, no family history of breast cancer, and no past history of chest wall radiation at a young age). This screening technique is no longer considered useful, based on the evidence.
- Mammograms in average-risk women are strongly recommended annually for women aged 45 to 54. Such a recommendation is made as a strong guideline and is without reservation. Women may elect to begin mammography for screening annually from age 40 to 44, but the risks as contrasted to the benefits should be discussed. This recommendation is considered "qualified" as the risk-benefit issue may be in dispute. Women over 55 also of average risk and asymptomatic can consider going to mammography every two years or yearly as they prefer. Such a recommendation is still a "qualifed" one as opposed to a strong, evidence-based recommendation.
- Finally, mammography should continue as long as the woman is in overall good health with at least a 10-year life expectancy. Again, this is only a qualified recommendation.
Mammography is generally of greater benefit in older women than in younger women, because younger women frequently have more dense breasts, and there is a higher incidence of false-positive mammography results in younger women. The addition of ultrasound examination to screening mammography can be of value in screening younger women at higher risk or who have dense breast tissue.
Because of these limitations of mammography in younger women, the U.S. Preventive Services Task Force recommends that routine yearly screening mammography begin at age 50. Women aged 40 to 49 are encouraged to discuss their situation with their health-care practitioner to decide on the appropriate time to begin screening mammography.
Breast self-examination (BSE) is an option for women starting in their 20s. Women should report any breast changes to their health-care professional.
If a woman wishes to do BSE, the technique should be reviewed with her health-care professional. The goal is to feel comfortable with the way the woman's breasts feel and look and, therefore, the woman can detect changes in her breasts if they do not feel or look normal.
For some women at higher risk of developing breast cancer, the addition of MRI scanning is recommended as a screening tool. The American Cancer Society recommends that women at high risk for breast cancer (greater than 20% lifetime risk) receive an MRI and a mammogram every year. Women at moderately increased risk (15%-20% lifetime risk) should discuss the benefits and limitations of adding MRI screening with their health-care professional.
Women should discuss with their doctor about how often and when they should begin screening tests.
Definitive Breast Cancer Diagnosis
Even if imaging tests show an abnormality or are suspicious for breast cancer, definitive diagnosis requires obtaining a tissue sample for analysis. The technique of obtaining a sample is called a biopsy. A biopsy may be taken of a small area of the abnormality (an incisional biopsy), or the entire abnormal area may be removed at the time of biopsy (excisional biopsy). Biopsy allows the pathologist (a physician with special training in the diagnosis of diseases based on the characteristic appearance and analysis of tissue samples) to determine if cancer is present and, if so, what type of cancer. Biopsy also provides a tissue sample for further tests that are done (see below) to help determine the best type of treatment.
Specialized Breast Cancer Testing
Certain tests are routinely performed on breast cancer tumor samples to help determine the optimum type of treatment. These include the following:
- Hormone receptor status: Breast cancer tissue is tested to look for the presence of receptors for the hormones estrogen and progesterone. Tumors are termed estrogen receptor-positive (ER+) or progesterone receptor-positive (PR+) if these receptors are present. This means that tumor growth is responsive to hormonal changes and that hormone-directed therapies may be effective in stopping growth.
- HER2: Another standard test measures the overexpression of a protein called HER2 on the breast cancer cells. If a tumor is HER2-positive (HER-3+), targeted therapies against this protein may be given.
About 15% of women have breast cancers that do not express any of these tumor markers (ER, PR, or HER2). These tumors are called triple-negative breast cancers.
Additional laboratory tests may be useful for some types of tumors to help determine the prognosis and treatment plan. These include, for example, studies of cancer cell proliferation -- that is, how frequently the cancer cells appear to be actively growing and dividing, as well as studies gene expression in the particular tumor, or even blood tests to look for circulating tumor cells.
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American Cancer Society. "Breast Cancer Overview." <http://www.cancer.org/cancer/breastcancer/overviewguide/>.
Stopeck, Alison T. "Breast Cancer." Medscape.com. Sept. 16, 2014. <http://emedicine.medscape.com/article/1947145-overview#aw2aab6b2b7>.
United States. National Cancer Institute. "Breast Cancer." Sept. 26, 2012. <http://www.cancer.gov/cancertopics/wyntk/breast>.