title: Selective reporting biases in cancer prognostic factor studies.
abstract: BACKGROUND
  Nonreported and selectively reported information and the use of different definitions may introduce biases in the literature of prognostic factors. We probed these biases in a meta-analysis of a prognostic factor for head and neck squamous cell cancer (HNSCC) mortality that has drawn wide attention--the status of the tumor suppressor protein TP53.
  
  
  METHODS
  We compared results of meta-analyses that included published data plus unpublished data retrieved from investigators; published data; and only published data indexed with "survival" or "mortality" in MEDLINE/EMBASE, with or without standardized definitions. We also evaluated whether previously published meta-analyses on mortality predictors for various malignancies addressed issues of retrieval and standardized information. All statistical tests were two-sided.
  
  
  RESULTS
  For the 18 studies with 1364 patients that included published and indexed data, we obtained a highly statistically significant association between TP53 status and mortality. When we used the definitions preferred by each publication, the association was stronger (risk ratio [RR] = 1.38, 95% confidence interval [CI] = 1.13 to 1.67; P = .001) than when we standardized definitions (RR = 1.27, 95% CI = 1.06 to 1.53; P = .011). The addition of 13 studies with 1028 subjects that included published but not indexed data reduced the observed association (RR = 1.23, 95% CI = 1.03 to 1.47; P = .02). Finally, when we obtained data from investigators (11 studies with 996 patients) and analyzed it with all other data, statistical significance was lost (RR = 1.16, 95% CI = 0.99 to 1.35; P = .06). Among 18 published meta-analyses of 37 cancer prognostic factors, 13 (72%) did not use standardized definitions and 16 (89%) did not retrieve additional information.
  
  
  CONCLUSIONS
  Selective reporting may spuriously inflate the importance of postulated prognostic factors for various malignancies. We recommend that meta-analyses thereof should maximize retrieval of information and standardize definitions.
authors: Department of Hygiene and Epidemiology, School of Medicine, University of Ioannina, Ioannina, Greece.
authors: Panayiotis A
authors: PA
authors: Kyzas
authors: Konstantinos T
authors: KT
authors: Loizou
authors: John P A
authors: JP
authors: Ioannidis
mesh_terms: D000368:Aged; D014408:Biomarkers, Tumor / Q000032:analysis*; D002294:Carcinoma, Squamous Cell / Q000737:chemistry / Q000401:mortality* / Q000473:pathology; D016001:Confidence Intervals; D015340:Epidemiologic Research Design; D005260:Female; D006258:Head and Neck Neoplasms / Q000737:chemistry / Q000401:mortality* / Q000473:pathology; D006801:Humans; D008207:Lymphatic Metastasis; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D011237:Predictive Value of Tests; D011379:Prognosis; D017594:Publication Bias; D012107:Research Design; D018570:Risk Assessment; D012307:Risk Factors; D015996:Survival Rate; D016159:Tumor Suppressor Protein p53 / Q000032:analysis*; D014481:United States / Q000453:epidemiology
chemical_list: D014408:Biomarkers, Tumor; D016159:Tumor Suppressor Protein p53