The Current Status of the Delineation and Determination of the Targets and the Radiation Protocols for Nasopharyngeal Cancer with Intensity-Modulated Radiotherapy

摘要

IMRT has increased the local-regional control and decreased the complications from treating nasopharyngeal cancer(NPC). Therefore studying IMRT is important.CT and MRI are complementary,and their joint use is currently considered to be the optimal modality to delineate the extent of the primary spread of NPC.The key problem in delineation of the neck nodes is how to translate anatomic node regions into the CT boundaries.The consensus guideline which narrowed the gap among different cancer centers is recommended in delineating the boundary of the cervical lymph node regions.The definition of the NPC GTV is clear and almost the same among the main cancer centers in their IMRT planning protocols. The suggested biological dose to the GTV is close to or more than 80 Gy; the main differences are the definitions of the CTVs and their schemes for the prescribed dose,and also the dosage to the high cervical region is different among those centers.According to their long-term follow-up results,it is suggested that,besides adding 5~10 mm margins to the primary lesions, the immediate high-risk structures(including the entire nasopharyngeal cavity,retropharyngeal space,clivus,base of the skul,pterygoid plates and muscles,parapharyngeal space,the sphenoid and partial ethmoid sinuses, the posterior third of the maxillary sinuses and the nasal cavity)should also be included with a prescription of more than 60 Gy,and the bilateral Ib,II and Va node levels should be ranked as high-risk regions and differentialy prescribed for treatment with no less than 60 Gy.