title: Bridging the etiologic and prognostic outlooks in individualized assessment of absolute risk of an illness: application in lung cancer.
abstract: Assessment of individual risk of illness is an important activity in preventive medicine. Development of risk-assessment models has heretofore relied predominantly on studies involving follow-up of cohort-type populations, while case-control studies have generally been considered unfit for this purpose. To present a method for individualized assessment of absolute risk of an illness (as illustrated by lung cancer) based on data from a 'non-nested' case-control study. We used data from a case-control study conducted in Montreal, Canada in 1996-2001. Individuals diagnosed with lung cancer (n = 920) and age- and sex-matched lung-cancer-free subjects (n = 1288) completed questionnaires documenting life-time cigarette-smoking history and occupational, medical, and family history. Unweighted and weighted logistic models were fitted. Model overfitting was assessed using bootstrap-based cross-validation and 'shrinkage.' The discriminating ability was assessed by the c-statistic, and the risk-stratifying performance was assessed by examination of the variability in risk estimates over hypothetical risk-profiles. In the logistic models, the logarithm of incidence-density of lung cancer was expressed as a function of age, sex, cigarette-smoking history, history of respiratory conditions and exposure to occupational carcinogens, and family history of lung cancer. The models entailed a minimal degree of overfitting ('shrinkage' factor: 0.97 for both unweighted and weighted models) and moderately high discriminating ability (c-statistic: 0.82 for the unweighted model and 0.66 for the weighted model). The method's risk-stratifying performance was quite high. The presented method allows for individualized assessment of risk of lung cancer and can be used for development of risk-assessment models for other illnesses.
authors.affiliation: Department of Epidemiology and Biostatistics, Schulich School of Medicine and Dentistry, University of Western Ontario, Kresge Building K214, 5510 Richmond St., London, ON, N6A 5C1, Canada. ikarp@uwo.ca.|Department of Social and Preventive Medicine, School of Public Health, University of Montreal, Montreal, QC, Canada. ikarp@uwo.ca.
authors.forename: Igor
authors.initials: I
authors.lastname: Karp
authors.affiliation: Department of Social and Preventive Medicine, School of Public Health, University of Montreal, Montreal, QC, Canada.|Health Risks Division, Centre de recherche du CHUM, Montreal, QC, Canada.
authors.forename: Marie-Pierre
authors.initials: MP
authors.lastname: Sylvestre
authors.affiliation: Department of Epidemiology, Biostatistics and Occupational Health, McGill University, Montreal, QC, Canada.|Division of Clinical Epidemiology, Research Institute of the McGill University Health Centre, Montreal, QC, Canada.
authors.forename: Michal
authors.initials: M
authors.lastname: Abrahamowicz
authors.affiliation: ISPED, Centre INSERM U897-Epidemiology-Biostatistics, University of Bordeaux, Bordeaux, France.
authors.forename: Karen
authors.initials: K
authors.lastname: Leffondré
authors.affiliation: Department of Social and Preventive Medicine, School of Public Health, University of Montreal, Montreal, QC, Canada.|Health Risks Division, Centre de recherche du CHUM, Montreal, QC, Canada.
authors.forename: Jack
authors.initials: J
authors.lastname: Siemiatycki
mesh_terms: D002170:Canada / Q000453:epidemiology; D016022:Case-Control Studies; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000175:diagnosis / Q000453:epidemiology*; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D015203:Reproducibility of Results; D012107:Research Design; D018570:Risk Assessment; D012307:Risk Factors
keywords: Absolute risk; Case–control study; Etiologic research; Logistic regression; Lung cancer; Prognostic research; Prognostication; Risk assessment