Major salivary gland function in patients with radiation-induced xerostomia: Flow rates and sialochemistry

Radiation therapy for cancer of the head and neck region often causes salivary gland dysfunction and xerostomia. Several reports suggest that the submandibular/sublingual (SM/SL) glands may be less radiosensitive than the parotid. The purpose of this study was to evaluate differential radiation effects on the major salivary glands. Fifty patients with radiation-induced xerostomia were evaluated (33 males, 17 females; mean age 52.7). The average total tumor dose was 6034 cGy. Major salivary gland function was compared with that of 50 non-irradiated controls. Salivary flow rates included unstimulated and stimulated flows of both the parotid and SM/SL glands. Sialochemical analyses included total protein, lysozyme, lactoferrin, sodium, chloride, and potassium. All four measures of salivary flow were significantly reduced in patients as compared to controls (p = .0001). Like the parotid, submandibular/ sublingual gland dysfunction appears to be radiation dose- and field-dependent. Patients in the lowest radiation dose quartile (⩽ 5000 cGy) had significantly increased salivary flow compared to those in the highest dose quartile (⪖/ 6800 cGy; p = .025). Glands that were partially irradiated were more likely to have some residual function than fully irradiated glands ( p = .003). Lactoferrin content was increased in parotid saliva of radiation patients ( p = .0001). Chloride content was significantly increased also ( p = .0001). The SM/SL glands are clearly dysfunctional post-irradiation in xerostomia patients compared to controls, in terms of both flow rates and sialochemistry.