Breast cancer overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Assistant Editor(s)-In-Chief: Jack Khouri
Overview
Breast cancer is a cancer of the glandular breast tissue.
Epidemiology and Demographics
Worldwide, breast cancer is the fifth most common cause of cancer death (after lung cancer, stomach cancer, liver cancer, and colon cancer).[1] In 2005, breast cancer caused 502,000 deaths (7% of cancer deaths; almost 1% of all deaths) worldwide.[1] Among women worldwide, breast cancer is the most common cause of death due to cancer.[1]
In the United States, breast cancer is the third most common cause of cancer death (after lung cancer and colon cancer). In 2007, breast cancer caused approximately 40,910 deaths (7% of cancer deaths; almost 2% of all deaths) in the U.S.[2] Among women in the U.S., breast cancer is the most common form of cancer and the second- most common cause of cancer death (after lung cancer).[2] Women in the U.S. have a 1 in 8 lifetime chance of developing invasive breast cancer and a 1 in 33 chance of breast cancer causing their death.[3] A U.S. study conducted in 2005 by the Society for Women's Health Research indicated that breast cancer remains the most feared disease,[4] even though heart disease is a much more common cause of death amongst women.[5]
The number of cases has significantly increased since the 1970s, a phenomenon partly blamed on modern lifestyles in the Western world.[6][7] Because the breast is composed of identical tissues in males and females, breast cancer also occurs in males, although it is less common.[8]
Epidemiological risk factors for a disease can provide important clues regarding the etiology of a disease. The first work on breast cancer epidemiology was done by Janet Lane-Claypon, who published a comparative study in 1926 of 500 breast cancer cases and 500 control patients of the same background and lifestyle for the British Ministry of Health.
Today, breast cancer, like other forms of cancer, is considered to be the final outcome of multiple environmental and hereditary factors. Some of the effects of environmental and hereditary factors that ultimately cause breast cancer are:
- Lesions to DNA such as genetic mutations. Exposure to estrogen has been experimentally linked to the mutations that cause breast cancer.[9] Beyond the contribution of estrogen, research has implicated viral oncogenesis and the contribution of ionizing radiation.
- Failure of immune surveillance, which usually removes malignancies at early phases of their natural history.
- Abnormal growth factor signaling in the interaction between stromal cells and epithelial cells, for example in the angiogenesis necessary to promote new blood vessel growth near new cancers.
- Inherited defects in DNA repair genes, such as BRCA1, BRCA2 and p53.
Although many epidemiological risk factors have been identified, the specific cause of any individual breast cancer is often unknown. In other words, epidemiological research is able to provide information regarding the patterns of breast cancer incidence across certain populations, but not in a given individual. Approximately 5% of new breast cancers are attributable to hereditary syndromes, while no etiology is known for the other 95% of cases.[10]
The primary risk factors that have been identified are: sex,[11] age,[12] childbearing, hormones,[13] a high-fat diet,[14] alcohol intake,[15] obesity,[16] and environmental factors such as tobacco use and radiation.[17]
Diagnosis
Breast cancer is diagnosed by the examination of surgically removed breast tissue. A number of procedures can obtain tissue or cells prior to definitive treatment for histological or cytological examination. Such procedures include fine-needle aspiration, nipple aspirates, ductal lavage, core needle biopsy, and local surgical excision. These diagnostic steps, when coupled with radiographic imaging, are usually accurate in diagnosing a breast lesion as cancer. Occasionally, pre-surgical procedures such as fine needle aspirate may not yield enough tissue to make a diagnosis, or may miss the cancer entirely. Imaging tests are sometimes used to detect metastasis and include chest X-ray, bone scan, Cat scan, MRI, and PET scanning. While imaging studies are useful in determining the presence of metastatic disease, they are not in and of themselves diagnostic of cancer. Only microscopic evaluation of a biopsy specimen can yield a cancer diagnosis. Ca 15.3 (carbohydrate antigen 15.3, epithelial mucin) is a tumor marker determined in blood which can be used to follow disease activity over time after definitive treatment. Blood tumor marker testing is not routinely performed for the screening of breast cancer, and has poor performance characteristics for this purpose.
Treatment
The mainstay of breast cancer treatment is surgery during which the tumor is localized, with possible adjuvant hormonal therapy (with tamoxifen or an aromatase inhibitor), chemotherapy, and/or radiotherapy. At present, the treatment recommendations after surgery (adjuvant therapy) follow a pattern. This pattern is subject to change, as every two years, a worldwide conference takes place in St. Gallen, Switzerland to discuss the actual results of worldwide multi-center studies. Depending on clinical criteria (age, type of cancer, size, metastasis) patients are roughly divided to high risk and low risk cases, with each risk category following different rules for therapy. Treatment possibilities include: radiation therapy, chemotherapy, hormone therapy, and immune therapy.
In planning treatment, doctors can also use PCR tests such as Oncotype DX or microarray tests like MammaPrint that predict breast cancer recurrence risk based on gene expression. In February 2007, the MammaPrint test became the first breast cancer predictor to win formal approval from the Food and Drug Administration. This is a new gene test to help predict whether women with early-stage breast cancer will relapse in 5 or 10 years; this could help influence how aggressively the initial tumor is treated.[18]
References
- ↑ 1.0 1.1 1.2 World Health Organization (2006). "Fact sheet No. 297: Cancer". Retrieved 2007-04-26. Unknown parameter
|month=ignored (help) - ↑ 2.0 2.1 American Cancer Society (2007). "Cancer Facts & Figures 2007" (PDF). Retrieved 2007-04-26.
- ↑ American Cancer Society (2006). "What Are the Key Statistics for Breast Cancer?". Retrieved 2007-04-26. Unknown parameter
|month=ignored (help) - ↑ "Women's Fear of Heart Disease Has Almost Doubled in Three Years, But Breast Cancer Remains Most Feared Disease" (Press release). Society for Women's Health Research. 2005-07-07. Retrieved 2007-10-15.
- ↑ "Leading Causes of Death for American Women 2004" (PDF). National Heart Lung and Blood Institute. Retrieved 2007-10-15.
- ↑ Laurance, Jeremy (2006-09-29). "Breast cancer cases rise 80% since Seventies". The Independent. Retrieved 2006-10-09.
- ↑ "Breast Cancer: Statistics on Incidence, Survival, and Screening". Imaginis Corporation. 2006. Retrieved 2006-10-09. External link in
|work=(help) - ↑ "Male Breast Cancer Treatment - National Cancer Institute". National Cancer Institute. 2006. Retrieved 2006-10-16. External link in
|work=(help) - ↑ Cavalieri E, Chakravarti D, Guttenplan J; et al. (2006). "Catechol estrogen quinones as initiators of breast and other human cancers: implications for biomarkers of susceptibility and cancer prevention". Biochim. Biophys. Acta. 1766 (1): 63–78. doi:10.1016/j.bbcan.2006.03.001. PMID 16675129.
- ↑ Madigan MP, Ziegler RG, Benichou J, Byrne C, Hoover RN (1995). "Proportion of breast cancer cases in the United States explained by well-established risk factors". J. Natl. Cancer Inst. 87 (22): 1681–5. PMID 7473816.
|access-date=requires|url=(help) - ↑ Giordano, Sharon H (May 2004). "Breast carcinoma in men". Cancer. American Cancer Society. 101 (1): 51–57. Unknown parameter
|coauthors=ignored (help) - ↑ "Individual Risk Factors". BreastCancer.org. Retrieved 2007-03-11.
- ↑ Yager JD (2006). "Estrogen carcinogenesis in breast cancer". New Engl J Med. 354 (3): 270–82. PMID 16421368. Unknown parameter
|coauthors=ignored (help) - ↑ Chlebowski RT, Blackburn GL, Thomson CA, Nixon DW, Shapiro A, Hoy MK; et al. "Dietary fat reduction and breast cancer outcome: interim efficacy results from the Women's Intervention Nutrition Study (WINS)". J Natl Cancer Inst. 98 (24): 1767–1776. PMID 17179478.
- ↑ Boffetta, Paolo (2006-03-23). "The burden of cancer attributable to alcohol drinking". International Journal of Cancer. Wiley-Liss, Inc. 119 (4): 884–887. doi:10.1002/ijc.21903. PMID 16557583. Retrieved 2006-10-09. Unknown parameter
|coauthors=ignored (help) - ↑ BBC report Weight link to breast cancer risk
- ↑ ACS (2005). "Breast Cancer Facts & Figures 2005-2006" (PDF). Retrieved 2007-04-26.
- ↑ "FDA Approves New Breast Cancer Test". Associated Press, February 6, 2007.