Other Risk Factors
A previous premalignant breast biopsy Radial scars in benign breast biopsies
A history of breast cancer Exposure to ionizing radiation
Higher bone mineral density
Familial Risk Factors for Breast Cancer
More than 50% of women in family have breast cancer
Breast cancer present in more than I generation
Multiple occurrences of breast cancer (>3) in close relatives
Onset at less than age 45 years
History of bilateral breast cancer
High rate of co-existing ovarian cancer
B. Nulliparity and increased age at first pregnancy are associated with an increased risk for breast cancer. Nulliparity alone accounts for 16% of new cases of breast cancer each year. The relative risk for breast cancer increases with advancing age.
C. Race is an independent risk factor. While white women are at an increased risk for breast cancer, African American women with breast cancer have higher fatality rates and a later stage at diagnosis.
D. A family history of breast cancer, especially in first-degree relatives, increases the risk.
E. A history of breast cancer increases a woman's risk for subsequent breast cancers. If the woman has no family history of breast cancer, then the initial occurrence was sporadic, and the incidence for developing a second breast cancer is 1% per year. If the initial occurrence was hereditary, the incidence for developing a second breast cancer is 3% per year. Approximately 10% of women with breast cancer will develop a second primary breast cancer.
F. Familial or Genetic Risk Factors. A mutation in a tumor-suppresser gene occurs in 1 of 400 women and is located on chromosome 17q. Carriers of a BRCA1 mutation have an 85% lifetime risk of developing breast cancer. In addition, the risk of colon and ovarian cancers is also increased (40% to 50%) in these groups. The 70% of breast cancer patients who do not have inherited mutations on BRCA1 have mutations on BRCA2. The cumulative lifetime risk of breast cancer in a woman with the BRCA2 mutation is 87%.
G. Conclusions. Seventy-five percent of women with newly diagnosed breast cancer demonstrate no specific, identifiable risk factor. Most premenopausal breast cancer cases are genetically determined. In contrast, many postmenopausal cases are environmentally related.
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