People who have been treated for head and neck cancer have an increased chance of developing a new cancer, usually in the head and neck, esophagus, or lungs. The chance of a second primary cancer varies depending on the original diagnosis, but is higher for people who smoke and drink alcohol. Patients who do not smoke should never start. Those who smoke should do their best to quit. Studies have shown that continuing to smoke or drink (or both) increases the chance of a second primary cancer for up to 20 years after the original diagnosis.
Some research has shown that isotretinoin (13-cis-retinoic acid), a substance related to vitamin A, may reduce the risk of the tumor coming back in patients who have been successfully treated for cancers of the oral cavity, oropharynx, and larynx. However, treatment with isotretinoin has not yet been shown to improve survival or to prevent future cancers.This answer is based on source information from the National Cancer Institute