Whole-field intensity-modulated radiation therapy (IMRT) combined with replanning split-field IMRT for nasopharygeal carcinoma

We proposed an intensity-modulated radiotherapy (IMRT) technique: whole-field (WF) IMRT combined with replanning split-field (SF) IMRT in treating nasopharyngeal carcinoma (NPC) patients with the disease above the level of the larynx, and investigated its dosimetric consequences. Ten NPC patients were studied. Repeat CT imaging and replanning were performed at the time when the low anterior neck received a total dose of 50 Gy/25 fractions with WF-IMRT. Two treatment plans were created for each patient. Treatment plan A was generated from the first planning CT scan images, which included two portions (A1 and A2) for WF-IMRT and SF-IMRT, respectively; in treatment plan B, which also included two portions, the first portion B1 is identical to A1 but the second portion (B2) was generated from the second planning CT scan images. For both the planning target volumes of the gross tumor volume and the high-risk clinical target volume, the mean D₉₅ and V₉₃ were comparable between treatment plan A and B. However, the D_max to the spinal cord, brainstem and mandible, the D_mean and D₅₀ to parotid glands were all lower in treatment plan B as compared with treatment plan A. WF-IMRT combined with replanning SF-IMRT is a useful IMRT technique in treating NPC with the disease above the level of the larynx, which has a dosimetric superiority in terms of ensuring safe doses to normal organs and deserves clinic application.