Lung cancer is caused by smoking and other carcinogenic substances. It is the uncontrolled growth of abnormal cells in the lungs. While early lung cancer may cause no symptoms, later symptoms can include coughing, coughing up blood, chest pain, shortness of breath, and weight loss. Treatment options include surgery to remove cancerous parts of the lung, chemotherapy, and radiation therapy. Quitting smoking and avoiding secondhand smoke can help prevent lung cancer.