title: Assessment of cancer risk with β-interferon treatment for multiple sclerosis.
abstract: OBJECTIVE
  The risk of cancer after exposure to the β-interferons (IFNβs) for multiple sclerosis (MS) has not been established. We assessed whether IFNβ treatment for MS is associated with cancer risk or the risk of specific cancers in a population-based observational study.
  
  
  METHODS
  The British Columbia MS database was linked to the provincial Cancer Registry, Vital Statistics death files and Health Registration files. Using a nested case-control design, MS cancer cases were matched with up to 20 randomly selected MS controls at the date of cancer diagnosis by sex, age (± 5 years) and study entry year using incidence density sampling. Associations between treatment exposure and overall or specific (breast, colorectal, lung and prostate) cancers were estimated by conditional logistic regression, adjusted for MS disease duration and age. Tumour size at cancer diagnosis was compared between treated and untreated patients using the stratified Wilcoxon test to explore potential lead time bias.
  
  
  RESULTS
  The cohort included 5146 relapsing-onset MS patients and 48,705 person-years of follow-up, during which 227 cancers were diagnosed. Exposure to IFNβ was not significantly different for cases and controls (OR 1.28; 95% CI 0.87 to 1.88). There was a non-significant trend towards an increased risk of IFNβ exposure in the breast cancer cases (OR 1.77; 95% CI 0.92 to 3.42), but no evidence of a dose-response effect. Tumour size was similar between IFNβ treated and untreated cases.
  
  
  CONCLUSIONS
  There was no evidence of an increased cancer risk with exposure to IFNβ over a 12-year observation period. However, the trend towards an association between IFNβ and breast cancer should be investigated further.
authors.affiliation: Faculty of Medicine Division of Neurology, Multiple Sclerosis Program University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Elaine
authors.initials: E
authors.lastname: Kingwell
authors.affiliation: College of Pharmacy and Nutrition, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.
authors.forename: Charity
authors.initials: C
authors.lastname: Evans
authors.affiliation: Faculty of Medicine Division of Neurology, Multiple Sclerosis Program University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Feng
authors.initials: F
authors.lastname: Zhu
authors.affiliation: Faculty of Medicine Division of Neurology, Multiple Sclerosis Program University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Joel
authors.initials: J
authors.lastname: Oger
authors.affiliation: Faculty of Medicine Division of Neurology, Multiple Sclerosis Program University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Stanley
authors.initials: S
authors.lastname: Hashimoto
authors.affiliation: Faculty of Medicine Division of Neurology, Multiple Sclerosis Program University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Helen
authors.initials: H
authors.lastname: Tremlett
mesh_terms: D001955:British Columbia; D016022:Case-Control Studies; D016208:Databases, Factual; D005260:Female; D000068717:Glatiramer Acetate; D006801:Humans; D016899:Interferon-beta / Q000009:adverse effects* / Q000627:therapeutic use; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D009103:Multiple Sclerosis / Q000188:drug therapy*; D009369:Neoplasms / Q000139:chemically induced* / Q000175:diagnosis / Q000473:pathology; D010455:Peptides / Q000009:adverse effects* / Q000627:therapeutic use; D018570:Risk Assessment
chemical_list: D010455:Peptides; D000068717:Glatiramer Acetate; D016899:Interferon-beta