The Effect of Radiotherapy on the Excretion and Concentration Functions of the Salivary Glands

Salivary glands are often exposed to radiation during head and neck cancer radiotherapy (RT). In this study, the effect of radiation doses on concentration and excretion functions of salivary glands was investigated in patients receiving RT. Twenty-five patients were prospectively evaluated. The 99m Technetium (Tc-99m)-pertechnetate salivary gland scintigraphy was performed to each patient before RT (pre-RT), at the end of RT and 3rd month after RT (3rd month). Submandibular and parotid glands were separately evaluated. Scintigraphic evaluation of the submandibular glands didn't show any significant difference in mean cumulative doses on the concentration function at pre-RT, end of RT and 3rd month (p= 0.572). In excretion function there was a significant difference between pre-RT and 3rd month (p< 0.001); the end of RT and 3rd month (p= 0.006). When the dose was above 40 Gy, mild-moderate deterioration in the excretion function and when the dose was between 50-60 Gy, severe dysfunction was observed. For parotid glands; significant difference between pre-RT and end of RT (p< 0.001); pre-RT and 3rd month (p< 0.001) in concentration function was observed. When the dose was above 40 Gy, dysfunction was evident. Statistically significant difference was found in parotid glands' excretion function, between pre-RT and end of RT (p< 0.001); end of RT and 3rd month (p= 0.009); pre-RT and 3rd month (p< 0.001). With doses above 20 Gy, mild to moderate dysfunction and above 40 Gy, severe dysfunction was seen. For submandibular gland although the mean cumulative dose and the concentration function were not significantly related, the excretion function was significantly affected. There was a significant correlation between the mean cumulative dose of the parotid gland and its concentration and excretion functions.