Mapping Patterns Of Supraclavicular Nodal Metastases In Esophageal Cancer: Rethinking The Clinical Target Volume For High Risk Patients

Abstract

There is evidence-based evidence for prophylactic irradiation of supraclavicular region in radical radiotherapy of upper esophageal cancer. However, there is no clear definition of the extent of clinical target volume (CTV) in the supraclavicular drainage area of esophageal cancer. Our study aims to map the location of metastatic supraclavicular lymph nodes in esophageal cancer patients with supraclavicular node involvement, and determine whether and where the radiotherapy CTV of this region could be modified in upper esophageal cancer patients. We retrospectively reviewed our database of esophageal cancer patients who underwent radical radiotherapy from January, 2013 to December, 2019. Patients with metastatic or recurrent supraclavicular nodes were eligible for geographic mapping. All lymph nodes and their epicenters were registered proportionally by referencing surrounding landmarks onto simulation computed tomography (CT) images of a standard patient. A modified supraclavicular CTV with better involved nodes coverage and thus theoretically improved prophylaxis in this setting was tried and shown with upper esophageal cancer patient. A total of 138 patients were included in the study, and 103 with excellent images were selected for analysis. There are 240 positive lymph nodes in 103 patients. Bounded by the median line, 121 (50.4%) and 119 (49.6%) patients had lymph nodes in left and right supraclavicular sub-regions. Bounded by the border of sternocleidomastoid muscle, 132 (55.0%) and 108 (45.0%) patients had lymph nodes in medial and lateral SCV. There are 75(31.3%), 44(18.3%), 57(23.8%) and 64(26.7%) lymph nodes in the area of inner right, outer right, inner left, and outer left, respectively. The short diameter range of positive lymph nodes was 0.20-3.82cm, with the middle short diameter was 1.20cm and the average short diameter was 1.15cm. The infringement scope of most lymph nodes are as follows. For the lateral boundary, many lymph nodes infiltrate the space of the medial side of clavicle. For posterior boundary, many lymph nodes reach the prevertebral area, posterior boundary of clavicle section at the same level, the scalenus muscle space. At lower apical level, many lymph nodes reach the first rib and 1/2 rib space. We suggest the CTV borders may be as follows. The superior border is the inferior margin of cricoid cartilage, the lateral border reaches. The posterior border is posterior end of clavicle section. The posterior boundary needs to include the anterior and oblique muscle spaces. According to the distribution of supraclavicular lymph nodes, the extent of existing Atlases might not be adequate for potential metastatic sites especially on the left supraclavicular region. Extension of lateral and posterior CTV borders may be a reasonable approach to increase coverage.