title: [Pitfalls in the assessment of radioresponse as determined by tumor regression: consideration based on the location and histologic constitution of tumors].
abstract: OBJECTIVE
  To prove the following hypotheses regarding tumor shrinkage after radiotherapy. Tumors located on an outer tissue surface, e.g. esophageal tumors, shrink faster than parenchymal tumors, e.g. lymph-node metastasis, because two clearance mechanisms, exfoliation and absorption, can operate in the former type of tumors whereas only absorption can function in the latter. Tumors which are being controlled do not necessarily respond completely, because tumors are constituted not only of tumor cells but also stromal tissues that are difficult to be absorbed.
  
  
  METHODS
  Long-term shrinkage patterns of a parenchymal tumor were determined by using 18 curatively irradiated hepatomas. Preoperatively irradiated thymomas (10) and lymph-node metastases (37) from head and neck cancers were examined histopathologically. Twenty-one esophageal cancers were used for intra-patient response comparison between the primary disease and the lymph-node metastases.
  
  
  RESULTS
  Shrinkage patterns were generally biphasic: rapid exponential regression followed by a plateau phase. Histologically, thymomas generally consisted of predominant fibrous tissues and few remaining tumor cells. Radioresponse did not predict the presence of remaining cancer cells in the lymph nodes. Esophageal-cancer radioresponse was always higher for the primary disease than the lymph-node metastases.
  
  
  CONCLUSIONS
  The location and histologic constitution of tumors must be taken into account in predicting radiocurability using radioresponse.
authors.affiliation: Department of Radiology, University of Tsukuba.
authors.forename: K
authors.initials: K
authors.lastname: Ohara
authors.forename: W
authors.initials: W
authors.lastname: Shimizu
authors.forename: Y
authors.initials: Y
authors.lastname: Itai
mesh_terms: D006528:Carcinoma, Hepatocellular / Q000532:radiotherapy* / Q000556:secondary; D004938:Esophageal Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D006258:Head and Neck Neoplasms / Q000473:pathology / Q000532:radiotherapy; D006801:Humans; D008113:Liver Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D008207:Lymphatic Metastasis; D017063:Outcome Assessment, Health Care / Q000379:methods*; D013945:Thymoma / Q000532:radiotherapy / Q000556:secondary; D013953:Thymus Neoplasms / Q000473:pathology / Q000532:radiotherapy; D016896:Treatment Outcome