Table 1 Epidemiology of breast cancer: abbreviated risk factor summary

Well-confirmed risk factors

   Family history in first-degree relative or genetic predisposition (e.g. BRCA1)

   Height

   Benign breast disease

   Mammographically dense breasts

   Parity

   Age at first birth > 30 years versus at < 20 years

   Lactation (longer durations)

   Menopause at > 54 years versus at < 45 years

   High endogenous estrogen levels

   Postmenopausal hormone use

   Ionizing radiation exposure in childhood

   Menarche at < 12 years versus at > 14 years

   High body mass index (postmenopausal)

   High body mass index (premenopausal)^b

   Alcohol use (~1 or more drinks/day)

Probable relationship exists, based on substantial data

   Current oral contraceptive use

   Physical activity

Limited study to date

   High prolactin levels

   High premenopausal insulin-like growth factor I levels

   In utero exposures

   Nonsteroidal anti-inflammatory drug use