title: Modelling the distribution of health-related quality of life of advanced melanoma patients in a longitudinal multi-centre clinical trial using M-quantile random effects regression.
abstract: Health-related quality of life assessment is important in the clinical evaluation of patients with metastatic disease that may offer useful information in understanding the clinical effectiveness of a treatment. To assess if a set of explicative variables impacts on the health-related quality of life, regression models are routinely adopted. However, the interest of researchers may be focussed on modelling other parts (e.g. quantiles) of this conditional distribution. In this paper, we present an approach based on quantile and M-quantile regression to achieve this goal. We applied the methodologies to a prospective, randomized, multi-centre clinical trial. In order to take into account the hierarchical nature of the data we extended the M-quantile regression model to a three-level random effects specification and estimated it by maximum likelihood.
authors.affiliation: 1 Dipartimento di Economia, Metodi Quantitativi e Strategie d'Impresa, Università di Milano - Bicocca, Milan, Italy.
authors.forename: Riccardo
authors.initials: R
authors.lastname: Borgoni
authors.affiliation: 2 Clinical Trials and Biostatistics Unit, Istituto Oncologico Veneto IOV-IRCCS, Padova, Italy.
authors.forename: Paola
authors.initials: P
authors.lastname: Del Bianco
authors.affiliation: 3 Dipartimento di Economia e Management, Università di Pisa, Pisa, Italy.
authors.forename: Nicola
authors.initials: N
authors.lastname: Salvati
authors.affiliation: 4 Institute of Statistics and Econometrics, Freie Universität Berlin, Berlin, Germany.
authors.forename: Timo
authors.initials: T
authors.lastname: Schmid
authors.affiliation: 5 Department of Social Statistics and Demography, Southampton Statistical Sciences Research Institute, University of Southampton, Southampton, UK.
authors.forename: Nikos
authors.initials: N
authors.lastname: Tzavidis
mesh_terms: D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use; D056808:Biostatistics; D006801:Humans; D008137:Longitudinal Studies; D008545:Melanoma / Q000188:drug therapy*; D015233:Models, Statistical; D011446:Prospective Studies; D011788:Quality of Life; D012044:Regression Analysis; D057566:Self Report
keywords: Hierarchical data; Phase III study; Rotterdam Symptom Checklist; quantile regression; robust estimation