Target Volume Delineation After NACT in LA-NPCarcinoma Patients Treated With NACT+ CCRT

The gross tumor volumes of the primary site and the neck nodes (GTVnx and GTVnd) were delineated in accordance with the head and neck magnetic resonance imaging (MRI) and endoscopy, which obtained two weeks after the last cycle of NACT. The first clinical target volume (CTV1) was defined as the GTVnx plus a 5-10mm margin (2 to 3mm margin posteriorly) to encompass the high-risk sites of microscopic extension, the whole nasopharynx, and the location and extent of the primary tumor before NACT. The second clinical target volume (CTV2) was defined as the CTV1 plus a 5-10mm margin (2 to 3mm margin posteriorly) to encompass the low-risk sites of microscopic extension, the level of the lymph node located before NACT, and the elective neck area. The prescribed dose to GTVnx, GTVnd, CTV1 and CTV2 were 68Gy/30f, 62-66Gy/30f, 60Gy/30f and 54Gy/30f, respectively.