Etiology of Breast Cancer Disease

Breast cancer, like other forms of cancer, is considered to be a result of damage to DNA. Although many epidemiological risk factors, and biological co-factors and promoters have been identified, the majority of breast cancer incidence remains unattributable, and the primary cause is unknown.

All women and men are at risk for breast cancer, regardless of hereditary factors. In fact, 85 to 90 percent of breast cancer incidences cannot be explained by inherited genetic predisposition. Other known risk factors and personal characteristics include personal or family history of breast cancer, high breast tissue density, earlier onset of menstruation (12 years or younger), later menopause (55 years or older), late first-term pregnancy (30 years or older), no children or no breast-feeding, early or recent use of oral contraceptives, more than four years use of hormone replacement therapy, postmenopausal obesity, alcohol consumption, exposures to secondhand cigarette smoke and exposure to ionizing radiation. When all known risk factors and characteristics are added together including genetics and family history, as much as 50 percent of breast cancer cases remain unexplained. There is much more research in diagnosis and treatment of breast cancer than in its cause.

Age

The risk of getting breast cancer increases with age. For someone who lives to the age of 90, the chances of getting breast cancer is about 14.3% or one in seven during their lifetime. Men can also develop breast cancer, but their risk is less than one in 1000. 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.

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 disproportionately occurs 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 that it often is not detected by mammography or ultrasound. It presents with the signs and symptoms of a breast infection like mastitis.

Alcohol

Alcohol generally appears to increase the risk of breast cancer.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. The risk of breast cancer further increases with each additional drink consumed per day. The research also concludes that approximately 6% (between 3.2% and 8.8%) of breast cancers reported in the UK each year could be prevented if drinking was reduced to a very low level (i.e. less than 1 unit/week)."

Data from that research found that drinking alcohol moderately did not increase breast cancer risk. Breast cancer constitutes about 7.3% of all cancers. Among women, breast cancer comprises 60% of alcohol-attributable cancers. One study suggests that women who frequently drink red wine may have an increased risk of developing breast cancer.

"Folate intake counteracts breast cancer risk associated with alcohol consumption" and "women who drink alcohol and have a high folate intake are not at increased risk of cancer." Those who have a high (200 micrograms or more per day) level of folate (folic acid or Vitamin B9) in their diet are not at increased risk of breast cancer compared to those who abstain from alcohol. Foods rich in folate include citrus fruits, citrus juices, dark green leafy vegetables (such as spinach), dried beans, and peas. Vitamin B9 can also be taken in a multivitamin pill.

Environmental causes

Although environmental exposures are not generally cited as risk factors for the disease (except for diet, pharmaceuticals and radiation), a substantial and growing body of evidence indicates that exposures to certain toxic chemicals and hormone-mimicking compounds including chemicals used in pesticides, cosmetics and cleaning products contribute to the development of breast cancer. A recent Canadian study concluded that female farm workers are three times more likely to have breast cancer.

Genes

Two autosomal dominant genes, BRCA1 and BRCA2, have been linked to the rare familial form of breast cancer. People in families expressing mutations in these genes have a 60% to 80% risk of developing breast cancer according to Robbins Pathological Basis of Disease.

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 endogenous 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.

Combined oral contraceptive pills may produce a slight increase in breast cancer risk among long-term users, but this appears to be a short-term effect. 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. Breast cancer risk associated with hormonal contraceptive use did not appear to vary with family history of breast cancer.

Light levels

Researchers at the National Cancer Institute and National Institute of Environmental Health Sciences have concluded a study that suggests that artificial light can be a factor for breast cancer.

Obesity

Gaining weight after the menopause can increase a woman's or man's risk. Putting on 9.9kg (22lbs) increased the risk of developing breast cancer by 18%.

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. Darbre of the University of Reading has shown that aluminium salts increase estrogen-related gene expression in human breast cancer cells grown in the laboratory.

Some Traditional Chinese medicine doctors such as Dr. Hai-Sha Ni believe breast cancer is caused by clogged monthly milk secreting in women's bodies, which will transist to menstruate if no pregnancy happens in normal situations.

Source : wikipedia