Radiation-Induced Xerostomia: Objective Evaluation of Salivary Gland Injury Using MR Sialography

Xerostomia (dry mouth) is one of the serious complications of head and neck irradiation and has a strong influence on a patient's activities of daily living. MR sialography with salivary secretion stimulation provides additional functional information (salivary secretion reserve) and may contribute to the evaluation of the severity of xerostomia and predict the risk of developing a radiation-induced xerostomia. This aim of the study was to analyze MR sialography as an objective tool to evaluate radiation-induced salivary injury. MR sialography with salivary secretion stimulation was performed in 16 patients with head and neck malignancy before and after irradiation therapy. Multivariate (stepwise multiple regression) analysis was performed to analyze the nonstimulated and stimulated MR sialography findings and the clinical severity of xerostomia. Multivariate analysis of the preirradiation study revealed no significant independent variables that could predict the clinical severity of xerostomia. In the postirradiation study, following regression with 2 independent variables (secretion response of the submandibular gland [rSG] and parotid gland visualization on stimulated MR sialography [sPG]) could explain 70% of the cases: xerostomia severity grade = 0.681 + 0.871 x rSG - 0.471 x sPG. MR sialography is a useful method for visualization of salivary gland radiation injury and estimation of the severity of radiation-induced xerostomia. Insufficiency of secretion reserve at the irradiated submandibular gland has the strongest influence on xerostomia severity. Our investigation suggests that careful submandibular gland protection may lead to prevention and avoidance of radiation-induced xerostomia.