Crizotinib is a medication used to treat certain types of cancer, specifically for people with lung cancer that has a specific genetic mutation called ALK (anaplastic lymphoma kinase) or ROS1 (c-ros oncogene 1). It helps stop the cancer from growing and spreading in the body. Your doctor may prescribe Crizotinib if you have one of these genetic mutations and lung cancer to help control the disease and improve your quality of life.