The best prevention is making sure your water is pure, your diet clean, essential fatty acids are in the diet and you supplement with Lugol's iodine. Breast tissue needs large amounts of iodine at about 12.5mg per day. It will eliminate fibrocystic breast disease, and risk factor in getting breast cancer.. it will streghten your thyroid.. statistically too many women who get breast cancer are already on thyroid meds. You need to feed your thyroid not with synthetic hormones but with iodine... Lugols iodine.