title: Differences between clinical trial participants and patients in a population-based registry: the German Rectal Cancer Study vs. the Rostock Cancer Registry.
abstract: OBJECTIVE
  There are few data on whether the samples of randomized phase III studies are representative for cancer patients in general populations.
  
  
  METHODS
  We compared patient and disease characteristics of patients with stage II or III rectal cancer from the German Rectal Cancer Study (657 patients, 1995-2002) or the Rostock Cancer Registry (371 patients, 1997-2003). Differences between the Study and the Registry were analyzed for subgroups who received neoadjuvant chemoradiotherapy before resection or primary resection with or without postoperative chemoradiotherapy.
  
  
  RESULTS
  Study and Registry patients differed in age (median, 61.7 vs. 65.0 years, P < 0.001) and proportion of women (31.3 percent vs. 38.4 percent, P < 0.004). Significant age and gender differences were seen in primary resection but not in neoadjuvant subgroups. In neoadjuvant and in primary resection subgroups, Study participants were more likely than Registry patients to have tumor location in the lower third of the rectum, a higher rate of R0 resection, a greater number of lymph nodes assessed, and fewer T4 tumors. In the primary resection subgroups, Study participants were more likely to have received postoperative chemoradiotherapy. Multivariate analyses showed no effect of population type (Study vs. Registry) on disease-free or overall survival in neoadjuvant subgroups, but increased risk for Registry patients in primary resection subgroups.
  
  
  CONCLUSIONS
  Participants in clinical trials such as the German Rectal Cancer Study are not representative of all cancer patients of a general population. To enable wider extrapolation of results, future studies should include elderly and high-risk patients.
authors.affiliation: Cancer Registry, Department of Radiation Therapy, University of Rostock, Rostock, Germany.
authors.forename: Paul
authors.initials: P
authors.lastname: Kalata
authors.forename: Peter
authors.initials: P
authors.lastname: Martus
authors.forename: Heike
authors.initials: H
authors.lastname: Zettl
authors.forename: Claus
authors.initials: C
authors.lastname: Rödel
authors.forename: Werner
authors.initials: W
authors.lastname: Hohenberger
authors.forename: Rudolf
authors.initials: R
authors.lastname: Raab
authors.forename: Heinz
authors.initials: H
authors.lastname: Becker
authors.forename: Torsten
authors.initials: T
authors.lastname: Liersch
authors.forename: Christian
authors.initials: C
authors.lastname: Wittekind
authors.forename: Rolf
authors.initials: R
authors.lastname: Sauer
authors.forename: Rainer
authors.initials: R
authors.lastname: Fietkau