Dramatic and prolonged decrease of whole salivary secretion in nasopharyngeal carcinoma patients treated with radiotherapy.
OBJECTIVES: This study evaluates: (1) the change in whole salivary secretion rates of nasopharyngeal carcinoma patients before, during, and after radiotherapy, especially during the first week of irradiation; (2) the recovery capability of salivary glands up to 2 years postirradiation; and (3) the possible prognostic factors affecting salivary gland functions. STUDY DESIGN: Fifty patients who completed conventional radiotherapy using either once-per-day or hyperfractionated technique were included. Both unstimulated and stimulated whole salivary flow rates and ratios (flow rate compared with baseline) were measured before, during, 1, 3, and 6 months, and 1 and 2 years after radiotherapy. Multivariate analysis of potential prognostic factors affecting the salivary secretion ratio was made. RESULTS: Salivary glands were very radiosensitive and responded to radiation very early. After 720 cGy at the fourth day of the 8-week treatment, the unstimulated and stimulated salivary flow rates had decreased by 40%-50%. The nadir was reached in many patients after 3600 cGy (4 weeks). A second phase of decrease in salivary secretion was noted after completion of radiotherapy. CONCLUSIONS: Different mechanisms may be responsible for salivary response after low and high dose of radiation. This study shows no recovery of salivary secretion during the follow-up period, and the best strategy for managing radiation-induced salivary gland damage may be reduction of radiation dose to the glands.