US Pharm. 2019;44(9):13.
Metastases Pose the Main Threat
Breast cancer is a type of cancer that is marked by cells in the breast that begin to multiply at abnormally high rates. The cells typically involved in breast cancer are located in the glands that produce milk or in the ducts that carry milk out of the breast. Cancer that starts in the breast tissue can spread to other sites in the body, called metastasis. These sites include the bone, liver, lung, and brain. For those with breast cancer, it’s the metastasis that causes over 90% of cancer deaths. Early diagnosis of the disease can lead to a good prognosis and a high survival rate.
Early Detection and Treatment Are Key
According to the American Cancer Society, the average American woman has a 12% chance of developing breast cancer, making it the most common type of cancer among women next to skin cancer. Men can also develop breast cancer, with the average American male having a 1% risk for developing the disease. In North America, the 5-year average survival rate of breast cancer patients is above 80% due to early detection and treatment.
Breast Cancer Risk Factors
Many factors increase the probability of developing breast cancer, such as female sex, aging, estrogen levels, family history, gene mutations, and an unhealthy lifestyle.
Just being female significantly increases the risk for breast cancer. Female breast tissue fully forms during a narrow, 4-year period and remains highly active and responsive to hormones until the first full-term pregnancy. Male breast tissue only rarely fully forms and is generally exposed to less estrogen overall. Besides sex, the incidence of death from breast cancer is highly related to increasing age. With 99% of breast cancer–associated deaths occurring in women over the age of 40 years, regular screening should begin at age 40 years and continue as long as as the woman is in good health and is expected to live 10 years or longer.
Reproductive factors such as early menstruation, late menopause, late-age at first pregnancy, and never having been pregnant can also increase breast-cancer risk. Studies have shown that every 1-year delay in menopause increases the risk for breast cancer by 3%. Each 1-year delay in menstruation or each additional birth decreases the risk by 5% or 10%, respectively.
Genetic Factors Increase Predisposition
Nearly 25% of all breast cancer cases are related to family history. Women whose mother or sister had breast cancer are at a higher risk. Several genes have been associated with the risk for developing breast cancer. Breast cancer–associated genes 1 and 2 (BRCA1 and BRCA2) are two genes commonly screened for in women who are concerned about their genetic predisposition. Other genes tied to breast cancer risk include human epidermal growth factor receptor 2 (HER2), epidermal growth factor receptor (EGFR), and cMyc.
Exposures to estrogen that the body produces, as well as estrogen from external sources, are both associated with a higher risk for breast cancer. Treatment with oral contraceptive hormone replacement therapy (HRT) is the most common source of external estrogen. Even with improvements in newer oral contraceptives, the risk for breast cancer is still higher for African American and Iranian women. The general risk for breast cancer from oral contraceptive use decreases when it has not been used for 10 or more years.
Lifestyle Modification Can Help Prevent Breast Cancer
Modern lifestyles that include excessive alcohol intake and high levels of dietary fat intake can increase the risk for breast cancer. Alcohol consumption can elevate the level of estrogen-related hormones in the blood and activate the estrogen receptors in the body. Diets containing too much saturated fat are also associated with a poor prognosis and higher mortality in breast-cancer patients.
Screening tests are used to find cancer before a person has any symptoms. The American Cancer Society recommends that women aged 40 to 44 years start annual breast cancer screening with mammograms if they wish to do so. Women aged 45 to 54 years should get mammograms every year, and women aged 55 years and older should switch to mammograms every 2 years or continue yearly screening. Women should also know how their breasts normally look and feel and report any breast changes to a healthcare provider right away.
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