What causes breast cancer and who is at risk?

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The cause is unknown and may include several genetic, environmental, nutritional and hormonal factors. The following risk factors have been identified: * Female gender: 11% of women develop breast cancer. (European figures based on a life expectancy of 76 years) * Older age: 77% of women diagnosed with breast cancer are over 50. * Having one first-degree relative (mother, sister or daughter) with breast cancer doubles risk; having two increases risk five-fold. * Approximately 5-10% of breast cancers are the result of inherited mutations (changes) of the genes BRCA1 and BRCA2, which make proteins that help prevent cancerous growth. This cancer-preventing function is less effective with a mutated gene, and 50-60% of women with BRCA1 or BRCA2 mutations develop breast cancer by age 70. * Risk increases significantly if you have had cancer of the breast, ovaries, uterus or colon. Cancer in one breast means there is a 1% chance/year of developing cancer in the other breast. * When a biopsy indicates abnormal cells that are not yet cancerous (atypical hyperplasia), there is moderately increased risk of developing cancer in future. Atypical hyperplasia is a benign condition associated with abnormal growth of cells. A young patient with this diagnosis is very likely to develop a cancer. * Risk increases slightly if you have had a benign breast lump. * Having had chest area radiation therapy in childhood or youth increases risk. * Obesity (being overweight) is a possible risk, especially after menopause. * Diet high in saturated animal fats may increase risk. * Compared to non-drinkers, women who consume one alcoholic drink daily may have a small increase in risk; those who have two to five drinks daily have about 1.5 times the risk. * Exposure to estrogen increases risk. estrogen stimulates cell division: the more cells divide, the more likely it is that some may become cancerous. * Women with early onset of menstruation, late menopause, a menstrual cycle shorter or longer than average, no pregnancies or first pregnancy after 30, have slightly higher risk. * Using oral contraceptives may slightly increase risk. Women who stopped using oral contraceptives over 10 years ago do not appear to have increased risk. * More than 8 years of hormone replacement therapy (HRT) increases the risk. Risk returns to that of the general population within five years of stopping HRT. * Recent research suggests that smoking may increase the risk. Who gets breast cancer? As more women have mammograms and with improved detection and treatment options, rates of new cases and deaths from breast cancer have leveled off. Yet breast cancer is still the most common cancer in women. The disease is more common in older women, urban areas, higher socio-economic groups, unmarried women and Jewish women. Caucasians (especially of northern European descent) are slightly more at risk. Asian and Hispanic women have lower risk. Incidence in black women, specifically those of African descent, is increasing.