Protect the submandibular gland in patients with nasopharyngeal carcinoma treated with intensity-modulated radiotherapy: a preliminary study

Abstract

Objective To investigated the protective ways of intensity modulated radiotherapy (IMRT) for submandibular gland function in patients with nasopharyngeal carcinoma. Methods From March 2010 to November 2012, 101 patients with nasopharyngeal carcinoma were enrolled into study. They were treated with IMRT and evaluated by face to face dry mouth questionnaire during the follow-up of 3, 6, 12, 18, 24 and more than 24 months, meanwhile, their dose volume histogram of submandibular gland were taken into consideration. Results The average contralateral median dose and that of ipsilateral submandibular gland were (45.69±7.22) Gy and (51.64±8.20) Gy, respectively, and the V35, V40, V45, V50 were 95.82%, 69.99%, 46.90%, 25.50%, and 100 %, 96.50 %, 82.24 %, 60.98 %, respectively. There were positive relationship between the xerostomia grading of 3, 6, and 12 months after radiotherapy and the average dose of submandibular gland or the V35, V40, V45, V50. After 6 month, the xerostomia in 77.2 % (78/101) was significantly improved, and after 12 months, less than 5 % of patient complained about G3 or more grade of xerostomia. Conclusions When using IMRT in nasopharyngeal carcinoma, it's necessary to reduce the irradiated volume and the dose of submandibular gland. It is confined that the median dose of contralateral submandibular gland should be less than 40-45 Gy, and V40 or V45 ≤66.7 % or ≤50 %, which can effectively protect the function of salivary gland. Key words: Nasopharyngeal; Submandibular gland; Xerostomia; Intensity-modulated radiotherapy; Radiotherapy dosage