Abstract: Background and purpose: Radiotherapy has been the preferred method for the treatment of nasopharyngeal carcinoma (NPC). The aim of this paper was to compare the dosimetric differences in target volume and organ at risk between simplified intensity-modulated radiation therapy (sIMRT) and intensity-modulated radiation therapy (IMRT) in nasopharyngeal carcinoma. Methods: Treatment plans for ten NPC cases were designed with the same dose prescription and objective by means of IMRT and sIMRT respectively. Compare:(1) Plan dosimetric distribution, conformity index (CI) and homogeneity index (HI) of the targets, the dosimetric parameters of organ at risk (OAR); (2)The total monitor units (MU) and the total segments. Results: The CI and HI of the planning gross tumor volume(PGTV) were 0.647 and 0.057 (IMRT), 0.633 and 0.071 (sIMRT), respectively (t=2.14, P=0.062; t=-6.21, P=0.000). Compared to IMRT, sIMRT had less inferior target homogeneity. However both treatment plans could achieve the clinical dosimetric demands. There was no significant difference between IMRT and sIMRT in protecting OAR (t=-0.51-2.22, P=0.053-0.621). The sIMRT plan was better than IMRT plan in total MU and total segments. Conclusion: sIMRT is slightly inferior to IMRT in terms of target homogeneity, with similar target conformity and OAR dosimetric parameters. The sIMRT plan can reduce total monitor units and total segments. Thus it provides a clinical solution with high efficiency for radiotherapy center with a large number of patients.

Key words: Nasopharyngeal carcinoma, Radiotherapy, Simplified intensity-modulated radiation therapy, Dosimetry