Smoking increases the risk of many types of cancer (including cancers of the lung, kidney, and pancreas). Smoking causes a number of diseases and is linked to a higher risk of breast cancer in younger, premenopausal women. Smoking also can increase complications from breast cancer treatment, including damage to the lungs from radiation therapy, difficulty healing after surgery and breast reconstruction and the higher risk of blood clots when taking hormonal therapy medicines. Chemicals in cigarette smoke enter our bloodstream and can then affect the entire body. This is why smoking causes so many diseases, including at least 14 types of cancer, heart disease, and various lung diseases. Lung cancer survival is one of the lowest of all cancers and is the most common cause of cancer death. Smoking causes cancer is by damaging our DNA, including key genes that protect us against cancer. Many of the chemicals found in cigarettes have been shown to cause DNA damage, including benzene, polonium-210, benzo (a) pyrene and nitrosamines. Research also has shown that there may be the link between very heavy second-hand smoke exposure and breast cancer risk in postmenopausal women.