Refining the boundaries of the nodal CTV in the middle neck for nasopharyngeal carcinoma

Abstract Purpose In our previous research, we found that the subcompartments formed by the cervical fascia in the supraclavicular region (levels IV, Vb, and lower VI) effectively define the boundaries of the nodal clinical target volume (CTV) for nasopharyngeal carcinoma (NPC). This study aimed to determine whether the same anatomical approach could be applied to the middle neck region (levels III, Va, and upper VI). Materials and Methods We enrolled 100 patients with NPC who had positive lymph nodes throughout the neck, including the supraclavicular region. Their pretreatment images were systematically reviewed. We analyzed lymph node distribution patterns in relation to both the 2013 International Consensus node‐level definitions and the cervical fascia‐based subcompartments proposed in our previous study. Based on our findings, we recommend several modifications to the 2018 international CTV consensus guidelines. Results Our analysis confirmed that the cervical fascial subcompartments effectively define nodal CTV borders. Based on the observed lymph node distribution patterns, we propose several specific optimizations for the middle neck. The lateral border of level Va can be retracted from the skin and platysma to the line connecting the posterior margin of the sternocleidomastoid muscle (SCM) and the anterior margin of the trapezius muscle (TM). Medially, the border can be safely retracted to an anterior‐posterior line bisecting the center of the common carotid artery (CCA), as the space medial to this line is consistently devoid of nodes. In addition, the anterior boundary of the CTV may be defined by the lymph nodes located anterior to the carotid sheath; otherwise, the carotid sheath itself serves as the boundary. Conclusions Cervical fascial anatomy provides valuable insight into the distribution patterns of lymph nodes in the middle neck region in patients with NPC. Based on these anatomical considerations, appropriate modifications to the nodal CTV defined by the 2018 consensus can be implemented for the middle neck region.