Breast cancer is the most prevalent malignancy among women in the world today and has been particularly significant in the last 20 years. It is reported that the incidence of breast cancer in the United States has been increasing at an average annual rate of 3% since the 1980s, and in some western European and North American regions, the incidence of breast cancer has always ranked first among female malignant tumors. Although the incidence of breast cancer in China is a low incidence country in the world, there is an obvious increasing trend in recent years. Early diagnosis and early treatment can improve the survival rate and survival time. The high-risk susceptibility factors of breast cancer studied at home and abroad are as follows.
Age: Before menarche and 20 years old, the incidence is rare, about 0.2%, and increases rapidly after 20 years old, with a higher incidence at the age of 45-50.
2. Race: The lifetime risk of breast cancer is higher in white American women than in black women. The annual incidence of breast cancer among Asian-born Chinese women living in the United States is almost twice as high compared to women in mainland China, Singapore and Hong Kong.
3. Age at menarche and age at menopause: Early age at menarche (11 years or earlier) and later age at end of menopause (after 55 years) are established repeatable risk factors. Shorter menstrual cycles are consistent with a higher risk of breast cancer development. For each year of delayed menopause, the risk of breast cancer incidence increases by about 3%.
Repeatable risk factors include later age at first full-term pregnancy, infertility, and lower number of births in menstruating women. First full-term births over 35 years of age increase the risk of morbidity by about 5% for each year beyond that, while each subsequent increase in births decreases by 7%. Several studies have shown that shorter intervals between births are associated with a lower lifetime risk of developing breast cancer.
5. Breastfeeding: The total duration of breastfeeding is negatively correlated with the risk of breast cancer. It has been investigated that the risk of breast cancer is 2-3 times smaller in breastfeeding mothers than in non-breastfeeding mothers, and the longer the breastfeeding time, the less chance of breast cancer.
6. Weight: An increase of 5 kg in weight of older postmenopausal women increases the risk by 8%. After menopause, the C19 steroid androstenedione produced by the adrenal glands and postmenopausal ovaries is aromatized by aromatase in adipose tissue to produce estrone, which is utilized to transform into the more biologically active estradiol. The levels of estrone and estradiol in the blood are positively correlated with the weight of postmenopausal women, and this increase in estrogen levels with obesity is associated with an increased risk of breast cancer. The percentage of body fat, body fat weight and non-body fat weight of postmenopausal women increase the incidence of breast cancer, as a separate risk factor for breast cancer, while premenopausal women do not have this correlation,.
7. Height: Some scholarly analyses have shown that every 5 cm increase in height before menopause increases the risk of breast cancer. This may be related to the persistently higher levels of insulin-like growth factor in early life in taller people. Insulin-like growth factor is mainly regulated by growth hormone, and experiments have shown that growth hormone can increase the development of the breast, and secondly, it can regulate the downstream signaling system to promote cell proliferation and the invasion and metastasis of tumor cells.
8. Insulin and insulin-like growth factor levels: both have proliferation stimulating effects on normal and cancerous breast epithelial cells, in addition to inhibiting the synthesis of sex hormone binding protein (SHBG) and increasing the level of biologically active free estrogen. Insulin resistance and reduced concentration of SHBG lead to increased concentration of biologically active free estrogen may be one of the reasons for the increased risk of breast cancer in obese postmenopausal women.
9. Spiritual and psychological factors: Studies have shown that trauma, life misfortune, loneliness, depression, sulking and other adverse psychological and spiritual factors are related to the development of breast cancer. Studies have confirmed that the relative risk of breast cancer can be increased (2-3) times for women who have experienced serious adverse life events.
10, dietary structure changes: such as increased fat intake, reduced vegetable intake, etc., the results of the Harvard School of Public Health and other studies show that Asian postmenopausal women who prefer meat-sweet Western-style diet have a higher risk of breast cancer than those on a vegetable-soy diet. Also, frequent consumption of bacon, sausage and pickles is a risk factor for breast cancer. Reducing the intake of animal fats and sweets and consuming more green vegetables, soy products and fruits reduce the risk of breast cancer because vitamins D, A, C, E and carotenoids have protective effects on breast cancer. High fiber diet has a protective effect on breast cancer, and the more obvious its protective effect is as the intake increases.
11. Postmenopausal hormone replacement therapy: Hormone replacement therapy is the main method to prevent and treat perimenopausal syndrome, and also has a positive effect on improving osteoporosis in menopausal women. Post-menopausal breast duct epithelial atrophy and mesenchymal cell reduction may have a tendency to proliferate again after estrogen supplementation. It is also believed that estrogen is not a carcinogenic factor in breast cancer, but it can be used as a mitogen to promote the fission of breast cells that have already undergone carcinogenesis under the influence of other factors.
12. The use of birth control pills by young women may increase the risk of breast cancer: it may increase the risk of breast cancer or cause the imbalance of estrogen metabolism to indirectly cause breast cancer.
Family history of breast cancer has a high risk of development: Individuals with certain genetic defects or immunodeficiency diseases will show a tendency to develop certain tumors, i.e. genetic susceptibility to tumors. Breast cancer caused by genetic mutations has the following clinical features: younger age of onset than in disseminated patients; high incidence of bilateral breast cancer; high incidence of related tumors, including ovarian, colon, prostate, and endometrial cancers. Hereditary breast cancer accounts for 5-10% of all breast cancer cases.
14. Patients with breast cancer on one side have a higher risk of developing breast cancer on the opposite side than normal: some scholars have studied the relative risk of breast cancer on the opposite side of patients who were first diagnosed with breast cancer and received radiotherapy at the age of less than 45 years old, because irradiation at a young age increases the risk of developing breast cancer on the opposite side.
15. Multiple chest fluoroscopies or chest radiographs, or exposure to ionizing radiation: Some studies have reported that the risk of breast cancer depends on the dose of radiation and age; proximity to a microwave oven at work is also a risk factor.
16. Chronic cystic hyperplasia with papilloma: There are various factors affecting the development of benign breast lesions (confirmed by breast biopsy) to breast cancer, including family history of breast cancer, post-biopsy interval and menstrual status. A positive family history of premenopausal atypical hyperplasia doubles the risk of subsequent breast cancer, but does not increase the risk of breast cancer in postmenopausal women.
17.Environmental factors: polycyclic aromatic hydrocarbons: such as automobile exhaust; organic solvents; aromatic amines; heterocyclic amine compounds, such as from high-temperature cooking fumes and in charred meat and fish.
18, oncogenes, oncogene suppressor mutations: 20%-30% of breast tumors have amplification of c-erbB-2 gene and overexpression of its coding receptor protein; 20%-40% of breast cancer patients have oncogene P53 mutation.
19.Other factors: Not many women are active smokers in China, but the situation of passive smoking is more serious, and it has been reported that passive smoking is a risk factor for breast cancer, which can increase the risk of breast cancer in women. Physical activity during adolescence and adulthood can reduce the incidence of breast cancer, but more physical activity has an independent effect only in adulthood. The relationship between the use of various drugs for hypertension, clothing dyes and hair dyes and the development of breast cancer is uncertain.
In conclusion, breast cancer occurs when multiple environmental factors act to mutate multiple genes, which eventually become tumor cells through multi-stage evolution. Factors influencing the formation of breast cancer include the role of genetics and environment (including diet), the influence of endogenous as well as exogenous hormones, and altered immune status. Our aim is to reduce the incidence of breast cancer through the analysis of risk factors, to achieve early detection, diagnosis and treatment, and to improve the cure rate.