Multiple primary malignancies in patients with head and neck cancer.

During the 15 years from 1967 to 1981, 3,162 patients with carcinoma of the head and neck were treated with radiation therapy. Among them, 262 patients (8.3%) developed two or more independent malignancies. There were 80 patients with prior cancer. The overall incidence of second malignancies in patients who had radiation therapy was 5.8%. The incidences were 8.9, 7.7, 5.2 and 1.7% of index cancer in the larynx, pharynx, oral cavity and paranasal sinus, respectively. Second primaries were observed in the head and neck (36%), digestive tract (35%), lung (19%) and the remaining 10% in other bodily sites. Of the 1,486 patients who survived for five years or more after radiation therapy, only 10 (0.7%) developed second malignancies within the previous radiation field.