title: Applying the Longitudinal Model from Item Response Theory to Assess Health-Related Quality of Life in the PRODIGE 4/ACCORD 11 Randomized Trial.
abstract: A new longitudinal statistical approach was compared to the classical methods currently used to analyze health-related quality-of-life (HRQoL) data. The comparison was made using data in patients with metastatic pancreatic cancer.
  
  
  
  Three hundred forty-two patients from the PRODIGE4/ACCORD 11 study were randomly assigned to FOLFIRINOX versus gemcitabine regimens. HRQoL was evaluated using the European Organization for Research and Treatment of Cancer (EORTC) QLQ-C30. The classical analysis uses a linear mixed model (LMM), considering an HRQoL score as a good representation of the true value of the HRQoL, following EORTC recommendations. In contrast, built on the item response theory (IRT), our approach considered HRQoL as a latent variable directly estimated from the raw data. For polytomous items, we extended the partial credit model to a longitudinal analysis (longitudinal partial credit model [LPCM]), thereby modeling the latent trait as a function of time and other covariates.
  
  
  
  Both models gave the same conclusions on 11 of 15 HRQoL dimensions. HRQoL evolution was similar between the 2 treatment arms, except for the symptoms of pain. Indeed, regarding the LPCM, pain perception was significantly less important in the FOLFIRINOX arm than in the gemcitabine arm. For most of the scales, HRQoL changes over time, and no difference was found between treatments in terms of HRQoL.
  
  
  
  The use of LMM to study the HRQoL score does not seem appropriate. It is an easy-to-use model, but the basic statistical assumptions do not check. Our IRT model may be more complex but shows the same qualities and gives similar results. It has the additional advantage of being more precise and suitable because of its direct use of raw data.
authors.affiliation: Biometrics Unit-CTD INCa, Institut régional du Cancer Montpellier (ICM) - Val d'Aurelle, Montpellier, France (AB, SG-B, CB-M)|Institut Montpelliérain Alexander Grothendieck, University of Montpellier, Montpellier, France (AB, CL)
authors.forename: Antoine
authors.initials: A
authors.lastname: Barbieri
authors.affiliation: National Quality of Life in Oncology Platform, France (AA, TC, FB)|Methodological and Quality of Life Unit in Oncology (EA 3181), Besançon, France (AA, FB)
authors.forename: Amélie
authors.initials: A
authors.lastname: Anota
authors.affiliation: National Quality of Life in Oncology Platform, France (AA, TC, FB)|Institut de Cancérologie de Lorraine, Nancy, France (TC)
authors.forename: Thierry
authors.initials: T
authors.lastname: Conroy
authors.affiliation: Biometrics Unit-CTD INCa, Institut régional du Cancer Montpellier (ICM) - Val d'Aurelle, Montpellier, France (AB, SG-B, CB-M)
authors.forename: Sophie
authors.initials: S
authors.lastname: Gourgou-Bourgade
authors.affiliation: Unicancer R&D, Paris, France (BJ)
authors.forename: Beata
authors.initials: B
authors.lastname: Juzyna
authors.affiliation: National Quality of Life in Oncology Platform, France (AA, TC, FB)|Methodological and Quality of Life Unit in Oncology (EA 3181), Besançon, France (AA, FB)
authors.forename: Franck
authors.initials: F
authors.lastname: Bonnetain
authors.affiliation: Institut Montpelliérain Alexander Grothendieck, University of Montpellier, Montpellier, France (AB, CL)|Université Paul-Valéry Montpellier 3, Montpellier, France (CL)
authors.forename: Christian
authors.initials: C
authors.lastname: Lavergne
authors.affiliation: Biometrics Unit-CTD INCa, Institut régional du Cancer Montpellier (ICM) - Val d'Aurelle, Montpellier, France (AB, SG-B, CB-M)
authors.forename: Caroline
authors.initials: C
authors.lastname: Bascoul-Mollevi
mesh_terms: D000328:Adult; D000368:Aged; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D009362:Neoplasm Metastasis; D010190:Pancreatic Neoplasms / Q000188:drug therapy / Q000473:pathology / Q000503:physiopathology*; D011788:Quality of Life
keywords: EORTC QLQ-C30; generalized linear mixed model; health-related quality of life; item response theory; longitudinal analysis