title: Three-dimensional conformal radiation for esophageal squamous cell carcinoma with involved-field irradiation may deliver considerable doses of incidental nodal irradiation.
abstract: BACKGROUND
  To quantify the incidental irradiation dose to esophageal lymph node stations when irradiating T1-4N0M0 thoracic esophageal squamous cell carcinoma (ESCC) patients with a dose of 60 Gy/30f.
  
  
  METHODS
  Thirty-nine patients with medically inoperable T1-4N0M0 thoracic ESCC were treated with three-dimensional conformal radiation (3DCRT) with involved-field radiation (IFI). The conformal clinical target volume (CTV) was re-created using a 3-cm margin in the proximal and distal direction beyond the barium esophagogram, endoscopic examination and CT scan defined the gross tumor volume (GTV) and a 0.5-cm margin in the lateral and anteroposterior directions of the CT scan-defined GTV. The PTV encompassed 1-cm proximal and distal margins and 0.5-cm radial margin based on the CTV. Nodal regions were delineated using the Japanese Society for Esophageal Diseases (JSED) guidelines and an EORTC-ROG expert opinion. The equivalent uniform dose (EUD) and other dosimetric parameters were calculated for each nodal station. Nodal regions with a metastasis rate greater than 5% were considered a high-risk lymph node subgroup.
  
  
  RESULTS
  Under a 60 Gy dosage, the median D mean and EUD was greater than 40 Gy in most high-risk nodal regions except for regions of 104, 106tb-R in upper-thoracic ESCC and 101, 104-R, 105, 106rec-L, 2, 3&7 in middle-thoracic ESCC and 107, 3&7 in lower-thoracic ESCC. In the regions with an EUD less than 40 Gy, most incidental irradiation doses were significantly associated with esophageal tumor length and location.
  
  
  CONCLUSIONS
  Lymph node stations near ESCC receive considerable incidental irradiation doses with involved-field irradiation that may contribute to the elimination of subclinical lesions.
authors.affiliation: Department of Radiotherapy, Tianjin Medical University Cancer Institute and Hospital, and Tianjin Key Laboratory of Cancer Prevention and Therapy, Tianjin, PR China.
authors.forename: Kai
authors.initials: K
authors.lastname: Ji
authors.forename: Lujun
authors.initials: L
authors.lastname: Zhao
authors.forename: Chengwen
authors.initials: C
authors.lastname: Yang
authors.forename: Maobin
authors.initials: M
authors.lastname: Meng
authors.forename: Ping
authors.initials: P
authors.lastname: Wang
mesh_terms: D002294:Carcinoma, Squamous Cell / Q000532:radiotherapy*; D004938:Esophageal Neoplasms / Q000532:radiotherapy*; D000077277:Esophageal Squamous Cell Carcinoma; D006801:Humans; D008198:Lymph Nodes / Q000528:radiation effects*; D015182:Lymphatic Irradiation; D011879:Radiotherapy Dosage; D020266:Radiotherapy, Conformal