Head and neck neoplasia following irradiation for benign conditions.

A retrospective review of 143 patients with head or neck tumors who had received radiation therapy in the head and neck area for benign conditions during childhood or adolescence was conducted. This included an analysis of 1,080 patients from the Evanston Hospital Irradiated Thyroid Evaluation Clinic, which was established to define the relationship between irradiation and the subsequent development of thyroid neoplasia. The data support the following concepts of irradiation-induced neoplasia: (1) The thyroid, parathyroid, and salivary glands can develop benign and malignant changes after irradiation for benign conditions, with latent periods averaging about 30 years; (2) Once a glandular abnormality within the irradiated field appears, the risk of other glands in the field developing neoplastic changes is significantly increased.