Epidemiology and Risk Factors for Breast Cancer

A. Breast cancer is the most common cancer in women

B. Approximately 185,000 new cases this year and 47,000 deaths

C. Etiology is unknown

D. Most cases are sporadic; about 10% are apparently hereditary

1. BRCA-1 gene now localized on 17th chromosome, long arm

2. BRCA-2 gene (probable) on chromosome 13

3. It is unclear what role mutations in these genes play in sporadic cases

Risk Factors for Breast Cancer
Factor	Direction of association
Demographic features
Female gender	Increase
Increased age	Increase
Oriental heritage	Decrease
Occidental residence	Increase
Characteristics of the menstrual cycle
Early menarche	Increase
Late menopause	Increase
Oophorectomy	Decrease
Characteristics of pregnancy
Early first birth (age <25y)	Decrease
Further births at age <25y)	Decrease
Late first birth (age >30y)	Increase
Further births at age (>30y)	Increase
Other characteristics
Family history of breast cancer	Increase
History of benign breast disease	Increase
Increased height	Increase
Increased weight	Increase
Use of replacement estrogens |	Increase
Exposure to ionizing radiation |	Increase
Alcoholic beverage consumption	Increase