Table 1.
The main destructive factors of breast cancer derived in accordance with[17]
| Factors | Association | Influence | Risk threshold | Further information |
|---|---|---|---|---|
| Age at menopause and menarche[18,19] | Production of steroid hormones in the ovary | Steroid hormones affect the function and development of the breast | Late age at menopause and early age at menarche increase the risk of breast cancer | Exposure to high concentrations of endogenous estrogens for long times |
| Nulliparity[20,21] | As a result of socioeconomic development, childbirth may be delayed | Delayed childbearing and nulliparity are both associated with the increment of BC risk. | Childbearing patterns could affect the burden of BC (later age at births and fewer children) | The mother’s age at birth and spacing may influence the risk of BC |
| Breastfeeding[22] | Breastfeeding makes it possible that cells with potential DNA damage to be shed, which reduces the risk of BC | The risk of BC would be decreased by breastfeeding | Breastfeeding for at least 6 months decreases the risk of BC by 53% among mothers | Increment in the breastfeeding time decreases the risk of BC |
| Exogenous hormones[23,24] | The combination of estrogen-progestogen contraceptives; estrogen- progestogen menopausal therapy could affect BC | Long-term use of oral contraceptives and estrogen therapy increases the risk of BC | Using estrogen-progesterone therapy increases the risk of BC by 7.6%. | Utilizing HRT increases the risk of BC |
| Personal history of breast cancer[25,26] | Personal history of BC increases the risk of an invasive cancer | - | Diagnosis of tumors 1-4 years after detection of estrogen receptor-positive primary breast cancer | - |
| Family history of breast cancer[27,28,29] | In about one-third of the cases, genomic sequences and susceptibility genes cause BC | Mutation of the BRCA2 gene is responsible for the most frequent hereditary syndrome in BC | The risk of BC for women with a first-degree relative with BC is twice | Cowden syndrome increases the risk of BC |
| Ionizing radiation[30] | Gamma or X radiation are known as the main causative agents for BC in women | Exposure to radiation for medical purposes | Having too many X-rays of the body increases the risk of BC | Exposure to radiation in older women causes a lower risk of BC than that in the younger women |
| Alcohol consumption[31] | Alcoholic consumption is a carcinogenic agent for BC | The level of estrogen will be increased due to the consumption of alcohol | Consumption of >35 g of alcohol per day | - |
| Obesity[32,33] | Obesity increases the risk of BC | Increment the rate of fat could increase the risk of BC due to rising estrogen levels | Any 5-kg/m2 increase in BMI increases the risk of BC by 33%. | - |
| Physical activity[34,35] | Physical activity decreases the risk of BC | Physical activity affects the metabolism of endogenous steroid hormone and the immune system | At least 3-hour physical activity per week decreases the risk of BC by about 4-10%. | Physical inactivity increases the risk of BC by 33% |
BC: Breast Cancer