Xerostomia, or oral dryness, is one of the most common complaints experienced by patients who have had
radiotherapy of the oral cavity and neck region. The hallmarks of radiation-induced damage are acinar
atrophy and chronic
inflammation of the salivary glands. The early response, resulting in
atrophy of the secretory cells without
inflammation might be due to radiation-induced apoptosis. In contrast, the late response with
inflammation could be a result of radiation-induced
necrosis. The subjective complaint of a dry mouth appears to be poorly correlated with objective findings of salivary gland dysfunction.
Xerostomia, with secondary symptoms of increased
dental caries, difficulty in chewing, swallowing and speaking, and an increased incidence of
oral candidiasis, can have a significant effect on the quality of life. At present there is no causal treatment for radiation-induced
xerostomia. Temporary symptomatic relief can be offered by moistening agents and saliva substitutes, and is the only option for patients without residual salivary function. In patients with residual salivary function,
oral administration of
pilocarpine 5-10 mg three times a day is effective in increasing salivary flow and improving the symptoms of
xerostomia, and this
therapy should be considered as the treatment of choice. Effectiveness of sialogogue treatment requires residual salivary function, which emphasizes the potential benefit from sparing normal tissue during irradiation. The hypothesis concerning the existence of early apoptotic and late necrotic effects of irradiation on the salivary glands theoretically offers a way of achieving this goal.