title: Exfoliative tumor clearance following radiotherapy estimated by comparing radioresponse between primary esophageal cancer and its lymph node metastasis.
abstract: OBJECTIVE
  We estimated the capacity for exfoliative mechanical clearance which could occur in shrinkage of esophageal tumors following radiotherapy; both mechanical clearance and phagocytotic biological clearance of another clearance mechanism could participate in primary diseases located on outer tissue surfaces, whereas only biological clearance can participate in lymph node metastases surrounded by normal tissues which prevent mechanical clearance.
  
  
  METHODS
  Twenty-one patients with primary esophageal cancer and lymph node metastasis both treated by radiotherapy with the same dose were reviewed. The extent of tumor shrinkage was estimated by measuring the size on computed tomography scans before and after radiotherapy. The capacity for biological clearance plus mechanical clearance (primary disease) or biological clearance alone (lymph node metastasis) was defined as the slope of a tumor shrinkage curve. The capacity for mechanical clearance was estimated by intra-patient subtraction.
  
  
  RESULTS
  Extent of tumor shrinkage was consistently greater in primary disease than in lymph node metastasis for each patient, showing significant correlation in extent of shrinkage between them. The capacity was smaller for mechanical clearance than for biological clearance as a whole, showing no correlation between them.
  
  
  CONCLUSIONS
  Mechanical clearance is highly likely to participate extra in the shrinkage of tumors located on outer tissue surfaces; therefore, these tumors will normally respond more highly than parenchymal tumors.
authors.affiliation: Department of Radiology, Tsukuba University Hospital, Institute of Clinical Medicine, University of Tsukuba, Tsukuba, Japan. ki-ohara@md.tsukuba.ac.jp
authors.forename: K
authors.initials: K
authors.lastname: Ohara
authors.forename: H
authors.initials: H
authors.lastname: Tatsuzaki
authors.forename: W
authors.initials: W
authors.lastname: Shimizu
authors.forename: S
authors.initials: S
authors.lastname: Sugahara
authors.forename: N G
authors.initials: NG
authors.lastname: Molotkova
authors.forename: Y
authors.initials: Y
authors.lastname: Itai
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002294:Carcinoma, Squamous Cell / Q000473:pathology* / Q000532:radiotherapy*; D004938:Esophageal Neoplasms / Q000473:pathology* / Q000532:radiotherapy*; D005260:Female; D006801:Humans; D008207:Lymphatic Metastasis; D008297:Male; D008875:Middle Aged; D016896:Treatment Outcome