If a woman has already had breast cancer, she has a greater chance of developing a new cancer in the other breast. Such a new, or 'second,' cancer arises from a completely different location and should not be confused with a cancer that has recurred (come back) or metastasized (spread) from another site. The likelihood of a new cancer increases by 0.5% to 0.7% each year after the original diagnosis. After 20 years, a woman has a 10% to 15% chance of developing a new breast cancer.

A previous diagnosis of lobular carcinoma in situ (a localized tumor) is associated with a 10% to 30% greater breast cancer risk, and a previous diagnosis of ductal carcinoma in situ is associated with a 30% to 50% greater risk.

Family History Of Breast Cancer

Approximately 85% of women with breast cancer do NOT report a history of breast cancer within their families. Of the remaining 15%, about one-third appear to have a genetic abnormality. The risk of breast cancer is about two times higher among women who have a first-degree relative (mother, sister, or daughter) with this disease. The risk is increased 4- to 5-fold if the relative's cancer was found before menopause (the end of menstruation) and involved both breasts. The risk also is increased if breast cancer occurs in several family generations.

Genetic Mutations

About 5% to 10% of all breast cancers are hereditary. Scientists have identified certain genetic mutations (permanent changes in genetic material) that place people at increased risk of breast cancer. To date, the genes that have been most studied include BRCA1 and BRCA2.

Hormones

Breast cancer risk is increased in women with the longest known exposures to sex hormones, particularly estrogen (female sex hormone). Therefore, breast cancer risk is increased in women who have a history of :-

early first menstrual period (before age 12),
late menopause (end of menstruation),
no pregnancies,
late pregnancy (after age 30), or use of
birth control pills (the 'Pill;' oral contraceptives - 'OCs').

It should be mentioned that the Pill's exact hazards are difficult to assess, since risk apparently disappears in women who have not used oral contraceptives for more than 10 years.

Estrogen replacement therapy (ERT), also known as hormone replacement therapy (HRT), is used by many older women to relieve the symptoms of menopause. Certain studies indicate that ERT may increase the risk of breast cancer after long-term use (10+ years). Yet there is no official consensus on ERT, because scientists also have found that the increase in breast cancer risk is eliminated within 5 years of stopping ERT. In addition, some researchers have reported an increased risk of breast cancer in women taking estrogen or estrogen plus progestin, whereas others have not. Because of these uncertainties - and the fact that ERT has a number of positive benefits (e.g., lowered risks of bone fractures and heart attack) - a physician should be consulted about risks and benefits before a person uses ERT.