title: Evaluating the combination of molecular prognostic factors in tumor radiosensitivity in rectal cancer.
abstract: OBJECTIVE
  The local recurrence ratio following surgery alone is higher in patients with rectal cancer than in those with colon cancer. Preoperative radiotherapy reduces the rate of local recurrence and improves the chances of survival in patients with resectable advanced rectal carcinoma. Identification of predictive indicators of radiosensitivity is useful in selecting patients best suited for preoperative radiotherapy and thus helps to avoid unnecessary preoperative treatment. We investigated whether the combination of Ku, p53, p21, and p16 predicted tumor radiosensitivity.
  
  
  METHODS
  We studied 96 cases with advanced rectal carcinoma. In preradiation biopsy specimens of tumor samples, all immunoreactive nuclei of cells stained positive for Ku, p53, p21, and p16 were evaluated by immunohistochemistry. The expression of p53, p21 and p16 in more than 5% of tumor cells were defined as positive, whereas both Ku70 and Ku86 protein in more than 70% of such cells were defined as Ku positive. The expression patterns of Ku, p53, p21, and p16 were examined for association with tumor radiosensitivity, which was determined according to the criteria of histopathologic assessment of radiotherapy effects.
  
  
  RESULTS
  Univariate analysis showed a correlation between the expression patterns of Ku, p53, p21, and p16 and tumor radiosensitivity, while multivariate analysis showed that the expression pattern of Ku and p16 significantly correlated with tumor radiosensitivity. The combination of Ku and p16, or Ku, p53, p21 and p16 was therefore a good predictive marker for tumor radiosensitivity.
  
  
  CONCLUSIONS
  These findings tend to support the hypothesis that the combination of Ku, p53, p21, and p16 expression after radiotherapy can act as a marker for radiosensitivity. Further investigation is needed, as the number of cases in this study was limited.
authors.affiliation: Department of Surgical Oncology, Faculty of Medicine, University of Tokyo, Tokyo, Japan. komuro@kt.rim.or.jp
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Komuro
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Watanabe
authors.forename: Giichiro
authors.initials: G
authors.lastname: Tsurita
authors.forename: Tetsuichiro
authors.initials: T
authors.lastname: Muto
authors.forename: Hirokazu
authors.initials: H
authors.lastname: Nagawa
mesh_terms: D000328:Adult; D000368:Aged; D014408:Biomarkers, Tumor / Q000032:analysis*; D002470:Cell Survival / Q000528:radiation effects*; D003131:Combined Modality Therapy; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000032:analysis; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000032:analysis; D004265:DNA Helicases / Q000032:analysis; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007124:Immunoenzyme Techniques; D000072200:Ku Autoantigen; D008297:Male; D008875:Middle Aged; D020360:Neoadjuvant Therapy; D009364:Neoplasm Recurrence, Local / Q000401:mortality / Q000517:prevention & control; D009367:Neoplasm Staging; D011379:Prognosis; D012004:Rectal Neoplasms / Q000401:mortality / Q000473:pathology / Q000532:radiotherapy* / Q000601:surgery; D012007:Rectum / Q000473:pathology; D015996:Survival Rate; D016896:Treatment Outcome
chemical_list: D014408:Biomarkers, Tumor; C493956:CDKN1A protein, human; D019941:Cyclin-Dependent Kinase Inhibitor p16; D050759:Cyclin-Dependent Kinase Inhibitor p21; D004265:DNA Helicases; C106893:XRCC5 protein, human; D000072200:Ku Autoantigen