What Are the Risk Factors for Metastatic Breast Cancer?

Judi Ebbert, PhD, MPH, RN | Sept 29, 2017

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Do you, or a family member, have a diagnosis of metastatic breast cancer (MBC) and are wondering what risk factors you or your loved ones should be aware of for possibly developing this advanced cancer? Read on to learn more.

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Main risk factors for MBC in women

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The lifetime risk of developing invasive breast cancer is one in eight. Risk factors cited by the Metastatic Breast Cancer Network include advancing age, being a woman, having BRCA 1/2 gene mutations, being of Ashkenazi (Eastern European) Jewish descent, having a first-degree relative with breast cancer, having been exposed to radiation, having had ductal carcinoma in situ (DCIS), and having dense breasts. Additional risks include stage at initial diagnosis and the tumor’s biological factors.

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Do risk factors for MBC differ from risk factors for earlier stage breast cancer?

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Yes. According to the Centers for Disease Control and Prevention (CDC), risk factors for earlier stage breast cancer in women include some of the same as MBC but also, some different: advancing age, genetic mutations in the BRCA1 and/or BRCA2 genes, starting menstruation prior to age 12, late or no pregnancy, onset of menopause after age 55, being inactive physically, and being overweight or obese after menopause.

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Other differences in risk between MBC and earlier stage breast cancer

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The CDC says other risk factors for earlier stage breast cancer in women are: having dense breasts, using combination hormone therapy, taking oral contraceptives, personal or family history of breast cancer, personal history of noncancerous breast diseases, previous treatment that involved radiation therapy to the chest, having taken or being the daughter of a mother who took diethylstilbestrol (DES) between 1940 and 1971, and heavy use of alcohol.

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Yes, men have MBC too (but it's rare)

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While metastatic breast cancer is most common in women, a small number of men have breast cancer that has spread to other parts of the body. Less than 1 percent of all breast carcinomas occur in men, according to the National Cancer Institute. Estimated deaths caused by metastatic breast cancer in 2017 in men totaled 460 and in women totaled 40,610.

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What are the risk factors for breast cancer in men?

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According to the American Cancer Society, risk factors for breast cancer in men are: aging, a family history of breast cancer; BRCA 1/2 gene mutations and CHEK2 and PTEN gene mutations; Klinefelter syndrome, a congenital condition in which men have a Y chromosome plus at least two X chromosomes; radiation exposure; heavy alcohol intake; and liver disease.

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Additional risk factors for breast cancer in men

Other risk factors for men developing breast cancer are: estrogen therapy used to treat prostate cancer or in sex reassignment; obesity; removal of the testicles or having an undescended testicle(s); and occupations in hot environments such as steel mills or places with increased exposure to gasoline fumes.

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Why is age a risk factor?

The older one is, the higher the risk, for both women and men. That’s because the longer we live, the more we are exposed to environmental agents that may cause genetic damage. As we grow older, our bodies become less efficient at repairing genetic damage, which increases risk for mutations that may transition into cancer cells.

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Surveillance is important

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Regular surveillance is critically important for people with metastatic and nonmetastatic breast cancer, and screening mammograms are important for older people never diagnosed with breast cancer.

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What is ‘triple negative’ breast cancer?

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Three common receptors “feed,” or fuel, most breast cancers: estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor 2 (HER2). A receptor is the site where specific protein molecules sit on the surface of cells, binding with molecules such as hormones, antigens, or antibodies.

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Successful treatments

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Most of the successful treatments for breast cancer target one or more of the three common receptors (ER, PR, HER2). If a tumor lacks all three receptors, it is classified as triple negative breast cancer (TNBC). Between 15 percent and 20 percent of breast cancers in the U.S. are triple negative. TNBC occurs more frequently in younger women, black women, and women who are positive for the BRCA1 gene mutation. TNBC tends to grow and spread faster than other breast cancers.

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Future of treatment

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Research focused on TNBC treatments is a national clinical research priority. In fact, clinical research seeking newer treatments for metastatic breast cancer is a priority at major cancer centers as well as commercial pharmaceutical companies nationally and beyond.

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Tools for learning more about MBC risk

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Learn more about how to assess risk for MBC at these sites:

NEXT: How and Where Does Metastatic Breast Cancer Spread?