Age
The risk of getting breast cancer increases with age. A woman who lives to age 90 has a lifetime risk of about 14.3%, or one in seven. The probability of breast cancer rises with age, but breast cancer tends to be more aggressive when it occurs in younger people. One type of breast cancer that is especially aggressive and that occurs disproportionately in younger people is inflammatory breast cancer. It is initially staged as Stage IIIb or Stage IV. It also is unique because it often does not present with a lump, so it is often undetected by mammography or ultrasound. It presents with the signs and symptoms of a breast infection like mastitis, and the treatment is usually a combination of surgery, radiation, and chemotherapy.Sex
Men have a lower risk of developing breast cancer (approximately 1.08 per 100,000 men per year), but this risk appears to be rising.Heredity
In 5% of breast cancer cases, there is a strong inherited familial risk. Two autosomal dominant genes, BRCA1 and BRCA2, account for most of the cases of familial breast cancer. Family members who harbor mutations in these genes have a 60% to 80% risk of developing breast cancer in their lifetimes. Other associated malignancies include ovarian cancer and pancreatic cancer. If a mother or a sister was diagnosed breast cancer, the risk of a hereditary BRCA1 or BRCA2 gene mutation is about 2-fold higher than those women without a familial history.In addition to the BRCA genes associated with breast cancer, the presence of NBR2, near breast cancer gene 1, has been discovered, and research into its contribution to breast cancer pathogenesis is ongoing. Commercial testing for BRCA1 and BRCA2 gene mutations has been available since at least 2004.
Diet
Dietary influences have been proposed and examined, and recent research suggests that low-fat diets may significantly decrease the risk of breast cancer as well as the recurrence of breast cancer. Another study showed no contribution of dietary fat intake on the incidence of breast cancer in over 300,000 women.Breast Cancer and Sprouts
In a study published in the Journal of the American Medical Association, biomedical investigators found that Brassica vegetable intake (broccoli, cauliflower, cabbage, kale and Brussels sprouts) were inversely related to breast cancer development. The relative risk among women in the highest decile of Brassica vegetable consumption (average 1.5 servings per day) compared to the lowest decile (virtually no consumption) was 58%. That is women who consumed the most Brassica vegetables were 58% less likely to develop breast cancer.A significant environmental effect is likely responsible for the different rates of breast cancer incidence between countries with different dietary customs. Researchers have long measured that breast cancer rates in an immigrant population soon come to resemble the rates of the host country after a few generations. The reason for this is speculated to be immigrant uptake of the host country diet. The prototypical example of this phenomenon is the changing rate of breast cancer after the arrival of Japanese immigrants to America.
Alcohol
Alcohol appears to increase the risk of breast cancer, though meaningful increases are limited to higher alcohol intake levels. Breast cancer constitutes about 7.3% of all cancers. Among women, breast cancer comprises 60% of alcohol-attributable cancers.The Committee on Carcinogenicity of Chemicals in Food, Consumer Products Non-Technical Summary concludes, "the new research estimates that a woman drinking an average of two units of alcohol per day has a lifetime risk of developing breast cancer 8% higher than a woman who drinks an average of one unit of alcohol per day.
Obesity
Gaining weight after menopause can increase a woman's risk. A recent study found that putting on 9.9kg (22lbs) after menopause increased the risk of developing breast cancer by 18%.Hormones
Persistently increased blood levels of estrogen are associated with an increased risk of breast cancer, as are increased levels of the androgens androstenedione and testosterone.Increased blood levels of progesterone are associated with a decreased risk of breast cancer in premenopausal women. A number of circumstances which increase exposure to estrogens including not having children, delaying first childbirth, not breastfeeding, early menarche (the first menstrual period) and late menopause are suspected of increasing lifetime risk for developing breast cancer.
Hormonal contraceptives may produce a slight increase in the risk of breast cancer diagnosis among current and recent users, but this appears to be a short-term effect.
A study of breast cancer diagnosis among current combined oral contraceptive pill users showed that 10 or more years after stopping, no difference was seen. Further, the cancers diagnosed in women who had ever used hormonal contraceptives were less advanced than those in nonusers, raising the possibility that the small excess among users was due to increased detection. The relative risk of breast cancer diagnosis associated with current and recent use of hormonal contraceptives did not appear to vary with family history of breast cancer.
