Synchronous and metachronous head and neck carcinomas.

Background: The incidence of head and neck cancer is increasing. To improve the survival of head and neck cancer patients, an effective program of screening and/or chemoprevention of second malignancies is essential. An analysis of the incidence, time to development, and risk factors of second malignant tumors in head and neck cancer patients can contribute to the design of effective screening and chemoprevention programs.