Breast Cancer basics

Breast cancer is cancer of breast tissue. Worldwide, it is the most common form of cancer in females, affecting approximately one out of eleven to twelve women at some stage of their life in the Western world. Although significant efforts are made to achieve early detection and effective treatment, about 20% of all women with breast cancer will die from the disease, and it is the second most common cause of cancer deaths in women.

Epidemiologic risk factors

It is important to have a model of causation of a disease in order to distinguish epidemiological risk factors or associations with disease, from the biological etiology and primary cause, secondary co-factors, and simple promoters of the disease given the underlying cause. By analogy in peptic ulcer disease, the cause is Helicobacter pylori, a co-factor is stomach acidity, a promoter may be aspirin which altogether produce a stomach ulcer. Each is a risk factor associated with disease, and one is the primary cause. The cause of breast cancer is not known.

Age

The risk of getting breast cancer increases with age. For a woman who lives to the age of 90 the chances of getting breast cancer her entire lifetime is about 12.5% or one in eight. Men can also develop breast cancer, but their risk is less than one in 1000 (see sex and illness). This risk is modified by many different factors. In a very small (~ 5%) proportion of breast cancer cases, there is a strong inherited familial risk. Some racial groups have a higher risk of developing breast cancer - notably, women of European and African descent have been noted to have a higher rate of breast cancer than women of Asian origin. However, these apparent racial differences diminish when geography is altered, as Asian women migrating to the western world, gradually acquire risk approaching that of western women.

The probability of breast cancer rises with age but breast cancer tends to be more aggressive when it occurs in younger women. One type of breast cancer that is especially aggressive and disproportionately occurs in younger women 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 that it often is not detected by mammography or ultrasound. It presents with the signs and symptoms of a breast infection like mastitis.

Genes

Two genes, BRCA1 and BRCA2, have been linked to the rare familial form of breast cancer. Women in families expressing mutations in these genes have a much higher risk of developing breast cancer than women who do not. Not all people who inherit mutations in these genes will develop breast cancer. Together with Li-Fraumeni syndrome (p53 mutations), these genetic aberrations determine around 5% of all breast cancer cases, suggesting that the remainder is sporadic. Genetic counseling and genetic testing should be considered for families who may carry a hereditary form of cancer.

Alcohol

Alcohol is another risk factor for the development of breast cancer. Women who drink half a glass of wine everyday have 6% increased risk of developing breast cancer.

Hormones

The International Agency for Research on Cancer (IARC) in Lyon, France invited 21 scientists from eight countries in June 2005, to evaluate the risk of cancer for humans of combined estrogen-progesterone contraceptives and combined estrogen-progesterone menopausal therapy. The working group found that there is a small increase in the relative risk of breast cancer in current and recent users of combined oral contraceptives.

The risk decreases to that of those who have never used such combined therapy ten years after cessation of use. The scientists described combined oral estrogen-progesterone contraceptives as "carcinogenic to humans." They also found an increased risk of breast cancer in women under treatment with combined menopausal therapy, which is confined mostly to current or recent users, increases with duration of use and exceeds that in women taking estrogen-only therapy.

Other

Other established risk factors include not having children, delaying first childbirth, not breastfeeding, early menarche (the first menstrual period), late menopause, obesity and taking hormone replacement therapy.

Unproven

It has been hypothesized that abortion may increase the risk of breast cancer because of hormones in early pregnancy. Recent large studies do not support this association.

Although not well quantified there has long been a concern about risk associated with environmental estrogenic compounds, such as dioxins, or phytoestrogens such as found in soy beans.

Aluminum salts such as those used in anti-perspirants have recently been classified as metalloestrogens. In research published in the Journal of Applied Toxicology, Dr. Philippa D. Darby of the University of Reading has shown that aluminum salts increase estrogen-related gene expression in human breast cancer cells grown in the laboratory.

Source - Wikipedia