title: The interaction between prognostic and pharmacodynamic biomarkers.
abstract: BACKGROUND
  Interactions between prognostic and pharmacodynamic (PD) biomarkers have received little attention.
  
  
  METHODS
  Prognostic and PD utilities were assessed with linear mixed-effects models using published data on repeated measurements of circulating caspase-cleaved (ctCK18) and total (tCK18) cytokeratin 18, in 57 patients with metastatic colorectal cancer undergoing chemotherapy.
  
  
  RESULTS
  The model for tCK18 (but not cCK18) separated the prognostic/PD interaction from the pure prognostic effect, illustrating the principle of dual prognostic and PD characteristics for a given biomarker.
  
  
  CONCLUSIONS
  These models provide the framework for the analysis and interpretation of longitudinal data to detect prognostic/PD biomarker interactions.
authors.affiliation: Department of Mathematics and Statistics, Fylde College, Lancaster University, Lancaster, UK.
authors.forename: L
authors.initials: L
authors.lastname: Bouranis
authors.forename: M
authors.initials: M
authors.lastname: Sperrin
authors.forename: A
authors.initials: A
authors.lastname: Greystoke
authors.forename: C
authors.initials: C
authors.lastname: Dive
authors.forename: A G
authors.initials: AG
authors.lastname: Renehan
mesh_terms: D014408:Biomarkers, Tumor / Q000378:metabolism*; D015179:Colorectal Neoplasms / Q000378:metabolism*; D006801:Humans; D053538:Keratin-18 / Q000032:analysis* / Q000378:metabolism; D011379:Prognosis
chemical_list: D014408:Biomarkers, Tumor; D053538:Keratin-18