Prevention is better than cure. Just read an article in http://breastcancer.dormitory.com/. It mentions that Walking Can Decrease Breast Cancer Recurrence 40 Percent.I think not just walking but better sleep and regular sports also help to decrease the posibility of breast cancer. Share the article as following hope it will help:

When it comes to further minimizing the chance of breast cancer recurrence, Dr. Carolyn Kaelin, a Harvard surgeon, breast cancer survivor and author of The Breast Cancer Survivor's Fitness Plan, says, "Brisk walking - about 3.0 mph on a treadmill - for three to five hours per week, or about 30 minutes a day, can net big benefits
for breast cancer survivors.