Primary tumor volume should be included in the TNM staging system of nasopharyngeal carcinoma.

TNM staging system based on anatomic location, cranial nerve and conventional radiation therapy is currently the widely used classification for nasopharyngeal carcinoma (NPC). However, the T classification in separation of primary tumor volume fail to predict the radiosensitivity of primary tumor. And with the advent of intensity-modulated radiation therapy (IMRT), increasing studies show the significance of the primary tumor volume on the treatment outcome of NPC patients and primary tumor volume significantly improve the prognostic validity of T classification in NPC. What's more, the current T staging system has limitations to provide appropriate treatment for different subgroup NPC patients. Therefore, we propose that primary tumor volume should be included in the TNM staging system of nasopharyngeal carcinoma to guide our clinical decision.