An Interpretation of International Guideline for Delineation of Clinical Target Volumes for Nasopharyngeal Carcinoma in 2017

Nasopharyngeal carcinoma (NPC), one of the carcinomas which can be radically cured by radiation therapy, is interested by radiologists. It is well known that the clinical target volumes (CTV) of radiotherapy and the dose are important factors affecting the prognosis of NPC. With the deepening of the research on the biological characteristics and the surrounding adjacent tissue structures of NPC, the existing guidelines may be difficult to meet the current needs for precision medicine. Therefore, international experts in this field made detailed consideration, exchanged opinions and finally published "International guideline for the delineation of the clinical target volumes (CTV) for nasopharyngeal carcinoma" on Radiotherapy and Oncology in 2018. The guideline suggested that CTVp1=GTVp+5mm margin, CTVp2=5mm expansion from CTVp1, CTVn1=GTVn+5 mm in cases with no extracapsular extension, and CTVn2=CTVn1+5mm expansion. Also, regarding adjacent structures in CTVp2, it made individual recommendations for the respective T-categories. What's more, it presented panel's discussions and consensus opinions on the delineation of the organs-at-risk (OARs) and other controversial areas. This article would like to try to interpret the details of this guideline.