An Initial Study On Relations Between Target Volume Delineation Of Upper Cervical Lymph Nodes Irradiation In Nasopharyngeal Carcinoma And Image-based Classification

BackgroundNasopharyngeal carcinoma (NPC) patients have high incidence of cervical nodes involvement, and radiotherapy is the main therapeutic method, which is especially important in cervical nodes irradiation. In 1999, Som et al. presented image-based classification and delineation of cervical nodes; And the European and North American cooperative groups reported the guidelines on CT-based delineation of lymph node levels and CTVs in the node-negative neck. But further study is needed to know whether the guidelines is suitable for the CTVs of cervical lymph nodes in patients with NPC treated by conformal radiotherapy, and how to use elective neck irradiationObjectiveTo explore the relations between target volume delineation of upper cervical lymph nodes irradiation in nasopharyngeal carcinoma and image-based classification.MethodsFrom Jan.2004 to Jun. 2005, 185 patients with NPC were retrospectively analyzed. The patients all underwent CT and MRI. Distribution of nodes involvement in different levels were assessed. The horizontal distance from midpoint of nodes involvement both to cervical lateral and to midline were measured; furthermore, the vertical distance from posterior edge of nodes involvement either to anterior edge of spinal cord or to posterior edge of spinous process were evaluated, including retropharyngeal lymph nodes(RLN)between the first cervical vertebra(C1) and lymph nodes in levelâ…¡b between the second cervical vertebra( C2) ; In the meantime, compare the different distribution of the lymphadenopathy in both levelâ…¡and RLN ,from C1 to the third cervical vertebra(C3).ResultsAmong the 185 patients, 158 present with nodes involvement, levelâ…¡nodes were the most frequently involved(87.5%), subsequently, the frequency of nodal metastases in RLN is 79.1%. From nodes involvement in levelâ…¡b to cervical lateral and to medline, the mean and median distance were 21.3mm, 21.0mm (14-31mm) and 44.5mm, 44.0mm(38-51mm), while to posterior edge of spinous process was 17.7mm, 18.0mm(0-30mm),respectively. But From metastatic nodes in RLN to cervical lateral and to medline, the mean and median distance were 49.2mm ,49.0mm(45-57mm) and20.9mm ,20.0mm(14-31mm), in addition to anterior edge of spinal cord was 14.8mm, 15mm(10-22mm), respectively. Lymph nodes involvement of levelâ…¡are almost distributed between C2 and C3 ,only 8%of which is at C1 , while retropharyngeal lymph nodes(RLN) are distributed almost between C1 and C2 , 4.2% of which is at C3.ConclusionsNodes in RLN and in levelâ…¡had a high incidence of involvement, and distributed in different sagittal planes. RLN and primary tumor were recommended to contour in one target volume.