Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Lung Cancer ?
    ### Response:
    Lung cancer is one of the most common cancers in the world. It is a leading cause of cancer death in men and women in the United States. Cigarette smoking causes most lung cancers. The more cigarettes you smoke per day and the earlier you started smoking, the greater your risk of lung cancer.
    