[Dosimetric verification and clinical efficacy of intensity modulated radiotherapy in nasopharyngeal carcinoma].

OBJECTIVE: To investigate dosimetric characteristics and to evaluate the clinical efficacy of intensity modulated radiotherapy (IMRT) as compared with conventional radiotherapy in nasopharyngeal carcinoma (NPC). METHODS: Forty-seven NPC patients who accepted IMRT served as the IMRT group, and conventional radiotherapy plan was also made for each patient in this group using the treatment planning system. Dosiological evaluation of the 2 radiotherapy plans was made through dose volume histogram, 95% target volume dose (V(95)) and normal tissue complication probability. Another 47 patients who underwent conventional radiotherapy (CRT) at the same period formed the control group. The therapeutic effect as well as the acutes and late toxicities of normal tissues in the 2 groups were observed. RESULTS: V(95) of the IMRT was more than 96% (96.83%-99.99%) for each target area, obviously superior to CRT in the sub-clinical target area. The radiation dose of normal tissues such as the brainstem and the spinal cord in the IMRT was much less than that in the CRT. Consistant with this, the part and complete remission rate, the 3-year loco-regional progress free survival rate, and overall survival rate in the IMRT group were all higher than those in the CRT group. For most patients in the IMRT group, the grade of acute toxicities was much lower than that in the CRT group. Patients in the IMRT group showed no more than grade 3 xerostomia, while in the CRT group still 21% of the patients suffered grade 3 or higher xerostomia a year later. CONCLUSION: Compared with CRT, IMRT can improve the target volume dose and decrease the dose of surrounding tissues, resulting in higher control rate and fewer side effects.