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.