Long-term effects of radiotherapy on taste and salivary function in man.

The long-term effects of radiotherapy on taste and salivary function were studied in 13 patients treated by radiation 1--7 years previously for tumors of the head and neck. Taste function was quantitatively evaluated using a standard forced choice, three-stimulus-drop technique for the determination of detection and recognition thresholds and a forced-scaling technique for the determination of taste intensity responsiveness. Parotid salivary function was quantitatively evaluated by determination of flow rate and protein secretion rate. Nine of the 13 patients studied (69%) had measurable taste loss; every patient who had radiotherapy including the parotid glands had measurable salivary dysfunction. Our results demonstrate that curative courses of radiotherapy for tumours of the head and neck may result in long-term changes in taste and salivary function. From the present study, the maximum tolerance doses resulting in a 50% complication rate 5 years after treatment (TD 50/5) are estimated to be 40--65 Gy for xerostomia and 50--65 Gy for taste loss. Therefore, in a standard treatment regimen for tumors of the head and neck, with curative intent, gustatory and salivary gland tissues frequently sustain maximum tolerance injury.