Investigation of radiosialadenitis during fractioned irradiation: sialoscintigraphical and histomorphological findings in rats

Xerostomia is the most debilitating side effect induced by irradiation of head and neck tumours and is caused by irradiation damage to the salivary glands. The aim of this study was to correlate structural histomorphological damages and sialoscintigraphical findings during fractioned radiotherapy. The head and neck area of 27 WAG/RijH rats was irradiated with Co-60-gamma rays (60 Gy/30f 6 weeks). To evaluate salivary gland function, a port system was implanted, and (99m) Tc-pertechnetat was applied at different stages of irradiation (0, 16, 30, 46, 60 and 6 months post-irradiation). In the course of treatment the parotid glands were examined histopathologically. Rat salivary glands developed a dose-dependent radiosialadenitis. After a dose of 16 Gy an intra- and extra-cellular oedema developed in the salivary glands. Progressive vacuolisation (30 Gy) developed into lipomatosis (46 Gy) and necrotic changes (60 Gy) in the parotid glands. Six months after irradiation treatment, the chronic histomorphological damages corresponded to stage II according to Seifert. The corresponding loss in gland function investigated by measurement of the (99m) Tc-pertechnetate uptake of the salivary glands was 13% (16 Gy), 26% (30 Gy), 57% (46 Gy), 75% (60 Gy) and 66.5% (6 months post-irradiation). The presented animal model is suitable to demonstrate the correlation of histomorphological and sialoscintigraphical findings.