BREAST CANCER (EPIDEMIOLOGY)
Breast cancer is the malignant growth of the cells that line the ducts and lobules in the breast. In 2007, there were over 180,000 cases of breast cancer in the U.S. and over 40,000 deaths due to breast cancer. It is the second most common type of cancer in women (second to skin cancer) in the U.S. and the most common cause of cancer in women worldwide. In the U.S., a woman born now as a 12% or 1 in 8 lifetime risk of developing breast cancer. African-American women have a higher incidence of breast cancer before 40 years, are more likely to be diagnosed with large tumors, and are more likely to die from breast cancer at every age. This may be due in part to more unequal access to medical care.
There are three dates in a woman’s life that have a major impact on breast cancer incidence, (1) age at menarche (i.e. first period), (2) age at first full-term pregnancy, and (3) age at menopause. Breast cancer is a hormone-dependent disease, which means that women without functioning ovaries who never receive estrogen replacement therapy do not develop breast cancer. This means that (1) women who experience menarche at an earlier age (< age 12) have a greater breast cancer risk than women who experience menarche later in life, (2) menopause occurring 10 years before the median age of menopause (52 years) reduces lifetime risk of breast cancer by 35% and lastly (3) women who have a first full-term pregnancy by age 18 have a 30-40% lower risk of breast cancer.
The role of diet in causing breast cancer is controversial. The exact role of fat in diet and increased caloric intake is breast cancer risk is unproven. However, increased caloric intake does lead to earlier menarche, later age at menopause and increased post-menopausal estrogen (this is because fatty tissue contains an enzyme called aromatase which is one of the main enzymes responsible for making estrogen).
Oral contraceptives cause little if any increased risk of breast cancer but they do offer substantial protective effects against ovarian and uterine cancer. On the other hand, the data surrounding hormone replacement therapy are far more controversial.
|BREAST CANCER IN WOMEN: FACTORS THAT INCREASE RELATIVE RISK|
Certain inherited genetic mutations for breast cancer
Two or more first degree relatives with breast cancer diagnosed at an early age
Personal history of breast cancer
High breast tissue density
|2.1-4||One first-degree relative with breast cancer
High-dose radiation to chest
High bone density
|1.1-2.0||Late age at first full-term pregnancy (>30 years)
Early menarch (<12 years)
Late menopause (>55 years)
No full term pregnancies
Never breast-fed a child
Recent oral contraceptive use
Recent or long-term use of hormone replacement therapy
Personal history of endometrium, ovarian or colon cancer
EVALUATION OF BREAST MASSES ON WOMEN AND MEN
As a result of improved treatment and earlier detection, mortality from breast cancer has begun to decrease substantially in the U.S. All women should be trained in breast self-examination. Although breast cancer in men is unusual, any lesion unilateral (occurring on one side) lesions in men should be examined in the same manner as in women. For early detection of breast cancer, the breast self-examination (BSE) is most useful when coupled with regular breast examination by an experienced clinician and mammography. The BSE is best done 5-7 days after menses when hormonal stimulation of breast tissue is low.
Patient instructions for BSE
1. Lie down with a pillow under your right shoulder. Place your right arm behind your head.
2. Use the finger pads of your three middle fingers on your left hand to feel for lumps in the right breast.
3. Press firmly enough to know how your breast feels. A firm ridge in the lower curve of each breast is normal. If you’re not sure how hard to press, talk with your health care provider.
4. Press firmly on the breast in an up-and-down pattern. You can use a circular or wedge pattern but use the same pattern every time. Check the entire breast area and remember how your breast feels form month to month
5. Repeat the examination on the left breast
6. If you find any masses, lumps or skin changes, see your doctor right away.
Repeat the examination of both breasts while standing with one arm behind your head. The upright position makes it easier to check the outer part of the breasts (toward your armpits). This is where about half of breast cancers are found.
For added safety, you may want to check your breasts by standing in front of a mirror. See if there are any changes in the way your breasts look such as dimpling of the skin, changes in the nipple, redness or swelling.
*Caveat: The above information is specific to epithelial breast cancer and does not consider lymphomas or sarcomas of the breast which are rare.
1. Harrison’s Principles of Internal Medicine. 17th ed. Chapter 86.
2. Bates Guide to Physical Examination and History Taking. 10th ed. Chapter 10.
3. American Cancer Society.