Delineation of neck clinical target volume specific to nasopharyngeal carcinoma based on lymph node distribution and the international consensus guidelines

Publication date: Available online 8 November 2017
Source:International Journal of Radiation Oncology*Biology*Physics
Author(s): Li Lin, Yao Lu, Xiao-Ju Wang, Hui Chen, Sha Yu, Jiao Tian, Guan-Qun Zhou, Lu-Lu Zhang, Zhen-Yu Qi, Jiang Hu, Jun Ma, Ying Sun
PurposeTo establish regional lymph node (LN) distribution probability map and draw neck clinical target volume (CTV) specific to nasopharyngeal carcinoma (NPC).Methods and MaterialsOne thousand patients with pathologically-proven NPC between January 2010 and December 2011 were enrolled. Center points of LNs with a minimal axial diameter (MID) ≥ 4 mm were marked on one single treatment planning computed tomography scan. Neck node levels I – X based on the 2013 updated international consensus guidelines were also contoured. LN distribution probability maps and distribution curves were established. Relationships between LN distribution and consensus guidelines were analyzed to propose modifications for CTV boundaries specific to NPC.ResultsA total of 10651 LNs from 959 patients were marked. Based on the distribution of LNs and consensus guidelines, the majority of node levels defined in the 2013 updated consensus guidelines were confirmed to be comprehensive and applicable for NPC. However, for level Vb, 13.3% (11/83) cases had LNs beyond the posteromedial border; for level VIIa (retropharyngeal LN), 1.5% (12/819) cases had LNs above the cranial boundary and 5 cases had LNs emerged in the medial group. Moreover, we confirmed that no LN had been detected in certain areas of level Ib, II, IVa and Vc. Accordingly, a new level VIIc was proposed to include medial group of retropharyngeal LNs, and moderate extended boundaries for levels Vb and VIIa were recommended, while reduced boundaries were possibly adaptable for levels Ib, II, IV and Vc.ConclusionThe majority of node levels in the 2013 updated consensus guidelines are comprehensive and applicable for NPC. While, we propose a new level VIIc to include medial group of retropharyngeal LNs, recommend moderate extended boundaries for levels Vb and VIIa, and suggested that boundaries for levels Ib, II, IV and Vc might be reduced.

Teaser

Neck node distribution probability maps and curves for NPC were established based on 10651 nodes from 956 patients. Relationships between node distribution and international consensus guidelines for delineation of neck node levels were analyzed. Our findings demonstrate that the majority of node levels in the 2013 updated consensus guidelines are comprehensive and applicable for NPC. We propose a new level VIIc to include medial group of retropharyngeal LNs, recommend moderate extended boundaries for levels Vb and VIIa, and suggest that boundaries for levels Ib, II, IV and Vc might be reduced.


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