Treatment protocol
The treatment protocol in our institution for patients with NPC includes radiation or chemoradiation therapy (CRT) according to the NCCN guidelines. Until 2008 2D/3D -CRT was the radiation modality available in our institution. Since 2008, intensity modulated radiation therapy (IMRT) has been the modality of choice.
A computed tomography simulation was used to plan treatment in all cases. Tumor volumes were outlined, and a computed tomography–based display of the isodoses was recorded to confirm adequate target coverage. The radiation field included the gross tumor in the nasopharynx and neck, elective nodal stations, with a planning target volume (PTV) of a 0.3-cm margin. In our study we examined in particular the radiation doses of the middle ear, Eustachian tube, Levator veli palatine and Tensor veli palatine muscles. Each radiation plan was accessed in AriaTM radiation planning software and the studied structures were delineated on each axial section of the simulation imaging. Corrections were later made on the sagittal and coronal sections of the imaging for a more precise outlining of the structures. (Figure 1.)