title: Deaths from breast cancer: tackling multidimensionality and non-linearity by correspondence analysis.
abstract: OBJECTIVE
  We investigated the use of non-linear, multidimensional factor analysis for the study of observational data on death from breast cancer. These data were obtained in the context of a clinical practice and not in a clinical trial. We looked into the correlations between patient characteristics and time of death and/or disease-free interval.
  
  
  METHODS
  We first analyzed the characteristics of a population of patients that had died from breast cancer (n = 295), then of a population including patients still alive 7 years after surgery (n = 344). We used correspondence analysis (CA) which is based on chi(2)-metrics, does not assume linear relationships, and provides graphic overviews.
  
  
  RESULTS
  The CA mapped variables (clinical stage, histoprognostic grade, node status, receptor positivity) in a way that fits in well with available knowledge on their importance as prognostic factors. We observed, however, that death occurred during three main periods (1-3, 4-7, < OR = 8 years after surgery) defined by different mixes of variables as if the disease progressed by stage rather than continuously. The CA distinguished long-term survivors (>7 years) from patients who died 8-10 years after surgery. Long-term survivors tended to be node-negative; those who died at 8-10 years tended to be the youngest patients (under 40).
  
  
  CONCLUSIONS
  Because correspondence analysis combines the advantages of multidimensional and non-linear methods, it is a valuable exploratory tool for describing multiple correlations within a population before attempting to establish statistical significance of selected variables by more classic methods.
authors.affiliation: Académie Méditerranéenne d'Oncologie Clinique, Marseille, France.
authors.forename: D
authors.initials: D
authors.lastname: Hans
authors.forename: T
authors.initials: T
authors.lastname: Ojasoo
authors.forename: J C
authors.initials: JC
authors.lastname: Doré
mesh_terms: D000328:Adult; D000368:Aged; D001943:Breast Neoplasms / Q000378:metabolism / Q000401:mortality* / Q000601:surgery; D005260:Female; D006801:Humans; D008875:Middle Aged; D015999:Multivariate Analysis; D017711:Nonlinear Dynamics; D011379:Prognosis; D011446:Prospective Studies; D011987:Receptors, Steroid / Q000378:metabolism; D015996:Survival Rate
chemical_list: D011987:Receptors, Steroid