The function of the parotid gland following radiation therapy for head and neck cancer

The parotid gland was selected for study of its salivary output before and after radiation therapy for head and neck cancer. Before radiation therapy, a sialogram of the parotid gland was performed with the patient's head positioned for radiation therapy; a lateral radiographic view of the parotid gland was used to compare with the radiation treatment portal to determine the portion of the parotid gland to he irradiated. Samples of stimulated saliva were collected from the parotid gland before and at 1 and 6 months post-radiation. Eighteen patients with head and neck cancer who received radiation therapy were studied. The data showed that in the irradiation of nasopharyageal, advanced oropbaryngeal and Waldeyer's ring lesions, 100% of the parotid gland was irradiated; for the early oropharyageal and hypopbaryugeal lesions, from 30 to 90% of the parotid gland was irradiated and for the supragiottic and oral cavity lesions, 25–30% of the parotid gland was irradiated. When 100% of the parotid gland was irradiated, no saliva was produced at 1 month post-radiation; this remained the same when re-tested at 4–8 months, however, when any portion of the parotid gland was not irradiated, there was residual salivary function.