Thursday 25 July 2013

Factors That Influence The Risk Of Breast Cancer

Factors that influence risk of developing breast cancer include:
  • Prior History of Breast Disease
  • Family History of Breast Disease
  • Age
  • Race
  • Reproductive and Menstrual History
  • Radiation Exposure
  • Dietary Factors
The relative effects of these and other risk factors in any given case of cancer is variable and very difficult to determine with accuracy at this time. Some of these and other risk factors are discussed on the following pages.
Prior History of Breast Disease
History of breast cancer, regardless of the type, greatly increases an individual's risk for future development of breast cancer. The second occurrence is most likely to be classified as invasive and ductal, rather than a lobular breast cancer. Such women are strongly advised to carefully monitor themselves and receive mammograms on a regular basis.
Family History of Breast Disease
It is possible to inherit defective genes that lead to the development of a familial form of a particular cancer type. Individuals with a family history of breast cancer are therefore at an increased risk of developing the disease. The degree of risk depends upon the type of relative affected. For example, risk is higher if an immediate family member has been diagnosed with breast cancer. The more closely related an individual is to someone with breast cancer, the more likely they will share the same genes that increased the risk of the affected individual. Risk also increases with the number of relatives affected.
Breast cancer risk is low before age 30 and increases with age, leveling off at the age of 80.
African American women are more likely to be diagnosed with early-onset (before age 45) breast cancer compared to white American women. This trend in incidence shifts, however, for women in their fifties. When comparing overall lifetime risk, African American women have a lower risk of developing breast cancer compared to white American women.
Cancer survival rates are greatly affected by the stage at which a cancer is detected. Early-onset cancers are generally more aggressive than cancers that develop later in life. Studies show that African American women have a greater chance of being diagnosed with high-grade and estrogen receptor (ER)-negative tumors. Regardless of their lower overall lifetime risk of developing the disease, African American women have a significantly higher chance of dying from breast cancer than any other ethnic group in the United States.
Reasons for these differences in cancer occurrence and death rate are still unclear. One explanation for the disparity is the socioeconomic differences that exist between ethnic groups. In this view, limited access to health care and clinical trials and the high cost of treatments may account for the higher African American breast cancer death rate. New investigations focused on biological differences, however, suggest that African Americans may develop tumors that are harder to treat. Current research seems to suggest that the disparity in cancer death rate is due to a combination of socioeconomic and genetic factors. Clearly, more work needs to be done in this area.
Reproductive and Menstrual History
Exposure to estrogen is associated with increased breast cancer risk. For this reason, women who experience menarche (begin their menstrual cycle) before age 12 and the onset of menopause at age 55 or older are at an increased risk of developing breast cancer.
On the other hand, women who carry pregnancy to full term at a young age have a decreased risk of developing breast cancer. During pregnancy, maternal hormone levels change drastically. Studies show that some of these hormones may provide anti-estrogen effects, protecting individuals from the negative effects of estrogen. Examples of proteins thought to impact cancer risk include:
  • Alpha-fetoprotein: Alpha-fetoprotein is a glycoprotein produced by the liver of a developing fetus. Since the protein is at its highest level during the third trimester, a pregnancy that is not carried to full term may not provide a protective effect.
  • Human Chorionic Gonadotropin (hCG): Human chorionic gonadotropin is a hormone produced by the placenta during pregnancy. The protein is elevated during the first trimester of pregnancy. Experiments with breast cancer cells suggest that the effects of hCG may partially explain the higher rate of breast cancer among nulliparous (non-child bearing) women.
Hormone Replacement Therapy
Hormone replacement therapy (HRT) is often prescribed to control menopausal symptoms that include decreased bone density, sexual dysfunction, fatigue, and mood swings. HRT may include treatment with estrogen alone or a combination of both estrogen and progesterone. Studies indicate that use of menopausal hormone therapy, currently or within the past five years, is associated with an increased risk of developing breast cancer. Several studies have shown that individuals who have stopped using HRT for more than five years are not at a significantly greater risk. Much of the information regarding HRT and breast cancer risks has come from population studies that may be difficult to compare with each other. The actual impact of HRT on breast cancer risk is still under investigation.
Exposure to Diethylstilbestrol
Diethylstilbestrol (DES) is a man-made estrogen that was prescribed between 1947 and 1971 to treat complications associated with pregnancy. Women who ingested this chemical during their pregnancy are at a slightly increased risk of developing breast cancer. Female offspring of women who were exposed to DES have a higher incidence of reproductive problems and cancers of the vagina and cervix.
Radiation Exposure
Exposure to radiation, such as radiation therapy used to treat Hodgkin lymphoma, increases risk of breast cancer throughout the remainder of a woman's lifetime. Relative risk depends on the age at which irradiation occurred, time since treatment, and radiation dose received. Women irradiated at a young age (before age of 30) are at an increased risk of developing breast cancer later in life compared to older women. Advances in therapeutic radiation techniques have resulted in the use of lower doses of radiation and exposure of smaller regions of the body. Such advances will hopefully reduce breast cancer risk due to irradiation therapy in years to come.
Dietary Factors
It is very difficult to identify dietary items that cause a particular cancer. Factors that may increase breast cancer risk include high fat intake, high alcohol consumption, and a diet rich in overcooked meats.
  • Alcohol: While studies indicate that consumption of one drink per day or less does not increase risk of breast cancer, there is evidence that heavy consumption of alcohol is associated with an increased risk. Findings show that women who consume an average of 4 or more drinks per day, regardless of the type of alcohol, may be at a 50% higher risk of breast cancer than those who do not drink alcohol.
  • Overcooked Meats: Heterocyclic amines are chemicals formed in the cooking process of meat products such as fish, beef, pork, and chicken. Exposure to high amounts of these chemicals, caused by a diet rich in broiled, grilled, or fried meat, has been correlated with increased risk of breast cancer in women

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