The incidence of malignant tumors is at a low level from 0 to 39 years old, and increases rapidly after 40 years old, and reaches a peak after 80 years old. So, which groups of people need to undergo early cancer screening? According to epidemiological survey, the following high-risk groups need early cancer screening: first, those who smoke more; second, those who have family history of tumor; third, those who have a history of tumor; fourth, those who have special jobs, such as long-term exposure to carcinogenic substances like arsenic, chromium, asbestos, nickel and cigarette smoke; fifth, those who have long-term chronic infectious diseases.