Optimization of cervical lymph node clinical target volume delineation in nasopharyngeal carcinoma: a single center experience and recommendation
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Li Li1,2, Yi Li1,2, Jun Zhang1,2, Qiuji Wu1,2, Haijun Yu1,2, Zheng Li1,2, Conghua Xie1,2, Yunfeng Zhou1,2 and Yahua Zhong1,2
1Department of Radiation and Medical Oncology, Zhongnan Hospital of Wuhan University, Wuhan, Hubei, China
2Hubei Cancer Clinical Study Center, Wuhan University, Wuhan, Hubei, China
Yahua Zhong, email: [email protected]
Keywords: nasopharyngeal carcinoma; intensity-modulated radiation therapy; cervical lymph node; clinical target volume
Received: August 21, 2017 Accepted: October 28, 2017 Published: June 05, 2018
Nasopharyngeal carcinoma (NPC) are characterized by distinct lymph node metastasis patterns. In order to minimize cervical lymph node irradiation volume, 379 NPC patients with metastatic cervical lymph nodes were eligible for geographic mapping. All lymph nodes were mapped into simulation computed tomography images of a template lymph node negative patient. The proportions of retropharyngeal lymph nodes (RLNs), Level Ib, II, III, IV, Va, Vb and supraclavicular (SCV) lymph nodes were 6.9%, 0.5%, 55.25%, 20.4%, 8.2%, 4.9%, 3.1% and 0.75%, respectively. Based on their distribution profile, we proposed the following modifications: 1. the lateral border of RLNs clinical target volume (CTV) be the medial edge of the internal carotid artery above the level of mastoid process, the medial border be adjacent to the cervical vessels below the free edge of the soft palate; 2. the submandibular gland should not be included in Level Ib; 3. Level II should include the posterior belly of digastric muscle, and the space between the posterior edge of submandibular gland and the anterior edge of sternocleidomastoid muscle; 4. the anterior border of Level III and IV should gradually shift backwards and the CTV only include part of the cervical vessels below the level where the thyroid gland appears; 5. the space of the posterior edge of trapezius muscle also should be included if there are metastatic lymph nodes in the transverse cervical vessle plexus. Our recommendations might adequately encompass metastatic lymph nodes while sparing the organs at risk and reducing adverse events.
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