Risk Factors for Breast Cancer
Prior history of breast diseases
The development of certain benign diseases of the breast in a woman is associated with increased risk of breast cancer. These conditions and associated risks are given below:
Prior personal history of breast cancer
- Ductal hyperplasia 1.5 to 2 fold increase
- Sclerosing Adenosis 1.5 to 2 fold increase
- Atypical Ductal Hyperplasia 4 to 5 fold increase
- Atypical lobular Hyperplasia 4 to 5 fold increase
- Lobular Carcinoma in situ 8 to 11 fold increase
If a woman has previously developed breast cancer, this would significant increase her risk for subsequent development of a second breast cancer. In some studies this risk is shown to be as high as about 1 percent per year from the time of the first breast cancer diagnosis. If the woman also has the BRCA1 or BRCA2 mutation then the risk would be increased to 5 percent per year. Patients who had some other types of cancers like, ovarian cancer, endometrial cancer and colon cancer may also have increased risk of breast cancer.
Menstrual and reproductive factors
The risk of development of breast cancer appears to be related to the number of years of exposure to the female hormone estrogen. Early onset of menstruation before the age of 12 years is associated with about 2-fold increase in the risk of breast cancer. Women who have premature menopause will have a reduction of risk of development of breast cancer. These women typically may have a 50 percent reduction in the risk of breast cancer. A full term pregnancy prior to age 30 is associated with decrease risk of breast cancer where as late first pregnancy or not having any pregnancy is associated with increased risk of breast cancer. The role of protective effect of lactation on breast cancer is not very clear, but there is some evidence to suggest that this may be the case.
More Resources on breast cancer