Risk Factors for Breast Cancer

• Age: Risk increases with age. Seventy-seven percent of women with breast cancer are older than 50 years at diagnosis; women aged 20-29 years represent less than 0.4% of the total.
  
  
• Genetics: Sixty to seventy percent of women with mutations of BRCA1 and BRCA2 genes will develop a breast cancer by age 70 years. Also mutations of the p53 gene increase the risk. In addition, some families without gene mutations have multiple family members in multiple generations with breast cancer. Women from such families are at an increased risk for developing breast cancer.
  
  
• Family history: Women who have a first-degree relative (sister, mother, or daughter) with breast cancer double the risk, and those who have 2 affected relatives multiply the risk 5 times.
  
  
• Medical history: A previous breast cancer increases risk (3-4 times) of developing a cancer in the same breast or in the opposite side.
  
  
• Fibrocystic breast disease does not increase the risk.
  
  
• Previous therapeutic irradiations always cause a meaningful increase in risk.
  
  
• Menstrual cycles: Early onset of menstruation (before age 12 years) or late menopause (older than 50 years) or both increases risk. 
  
  
• Pregnancies: No pregnancy, or first pregnancy after age 30 years, adds a low amount of risk.
  
  
• Estrogen replacement therapy for menopause: If taken for 10 years or more, estrogen after menopause can increase risk slightly. The risk is canceled 5 years after stopping the therapy. Ongoing studies, however, are showing mixed results on the risk or lack of risk by taking estrogen after menopause.
  
  
• Breastfeeding: According to some studies, breastfeeding for 1 1/2-2 years reduces risk.
  
  
• Alcohol: High consumption of alcoholic beverages increases risk.
  
  
• Smoking: Smoking does not seem to increase risk.
  
  
• Obesity: Being overweight increases risk.
  
  
• Physical activity: Movement and daily activity reduce risk and are therefore useful.