Importance: Although numerous studies have shown an association between alcohol consumption and cancer, how changes in drinking behavior increase or decrease the incidence of cancer is not well understood.

Question: How does the risk of developing cancer change after alcohol consumption is increased, stopped, or reduced?

Findings: In this cohort study of 4 513 746 insured adults in Korea, those who increased their alcohol consumption had a higher risk for alcohol-related cancers and all cancers compared with those who had sustained levels of drinking, whereas those who reduced their alcohol consumption had a lower risk. Although an increased risk was observed temporarily after quitting drinking, no increased risk was observed when quitting was sustained.

Meaning: Findings of this study suggest that drinking cessation and reduction should be reinforced for the prevention of cancer.