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Effect of fractionated radiotherapy on salivary gland function

The effect of fractionated radiotherapy on salivary gland function was studied by sialography and sialometry of parotid glands in four patients irradiated with 4000 or 6400 rads for malignant tumors of the head and neck region. Sialography was performed at the beginning and end of the irradiation period and 8 months later. By sialometry, the salivary secretion rate was determined after each irradiation treatment (a daily dose of 200 rads) during the whole treatment period and again 8 months later. The size of the glands was found to be unchanged at the end of the irradiation period despite the pronounced disturbance of the salivary secretion rate at this time. Thus it can be stated that the size of irradiated parotid glands is not a criterion of their function as in the case of normal glands. It was not possible to identify a critical dose level giving a pathologically low salivary secretion. Even after high doses in fractionated radiotherapy, a recovery of the parotid gland function has been found. Parotid glands on the “non‐tumor” side were irradiated with a dose of between 400 and 600 rads, and these small doses did not cause a reduction of salivary secretion rate below normal variation.