Abstract
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.
Highlights
Nasopharyngeal carcinoma (NPC) is one of the most common malignant tumors in south China [1,2,3,4]
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
Lymph node metastasis is of common occurence in NPC at early stage [21]. 36%–45% patients of NPC presented with the initial symptoms of neck lymphadenectasis, 60%-90% of them presents with cervical lymph node metastasis when newly diagnosed [22]
Summary
Nasopharyngeal carcinoma (NPC) is one of the most common malignant tumors in south China [1,2,3,4]. With the development of modern radiotherapy equipments, treatment planning systems and the application of intensity-modulated radiation therapy (IMRT), the 5-year survival rate of NPC has increased from 50% in the 1970s to 80% in the 2000s [6]. IMRT reduces some of the normal tissue complications such as mouth restriction [7], xerostomia [8, 9], radiation-induced brain injury [10, 11]. Certain complications including acute radiation-induced mucositis [12], swallowing pain [13], radiation-induced skin injury [14] are still prominent, probably because a part of the cervical lymph node target volumes are larger. The definition of the clinical target volume (CTV) of cervical lymph node in NPC is still in debate [14, 15]. While the Guidelines are proposed for all head and neck cancers, www.oncotarget.com
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