Purpose: Clinical target volumes (CTV) for radiotherapy (RT) in esophageal cancer (EC) are based on standard expansions\nof primary tumor volume. Data is needed to define regions at highest risk for occult disease, based on histology and\nlocation of the primary tumor. We therefore reviewed PET scans in EC patients to characterize the location of FDG-avid\nlymph node metastases (LNM).\nMaterials and methods: We identified 473 EC patients with reviewable pre-treatment PET-CT scans. Tumors\nwere classified by histology and location; 85% were distal or GE junction tumors and 71% were adenocarcinoma. FDGavid\nLNM were classified using standard radiographic nodal atlases, and distances from primary tumor to paraesophageal\nLNM were also measured.\nResults: The most common LNM in upper EC were supraclavicular, retrotracheal and paratracheal. The most common\nLNM in lower EC were paraesophageal and in the gastrohepatic space. Overall, 55% of paraesophageal LNM\nwere adjacent to primary tumor. Of upper esophageal tumors with paraesophageal LNM, 87% were adjacent\nto the tumor and none were >6 cm from tumor. However, 57% of lower esophageal tumors with paraesophageal\nLNM had non-adjacent paraesophageal nodes, 24% of which were >8 cm from the tumor.\nConclusion: A more data-driven and individualized approach to CTV delineation could improve the therapeutic ratio\nof RT in esophageal cancer. These results can guide CTV delineation by indicating the potential distribution of nodal\ninvolvement in esophageal cancer.
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