title: Malignancy incidence in 5294 patients with juvenile arthritis.
abstract: OBJECTIVE
  To determine cancer incidence in a large clinical juvenile-onset arthritis population.
  
  
  METHODS
  We combined data from 6 existing North American juvenile-onset arthritis cohorts. Patients with juvenile-onset arthritis were linked to regional cancer registries to detect incident cancers after cohort entry, defined as first date seen in the paediatric rheumatology clinic. The expected number of malignancies was obtained by multiplying the person-years observed (defined from cohort entry to end of follow-up) by the geographically matched age, sex and calendar year-specific cancer rates. The standardised incidence ratios (SIR; ratio of cancers observed to expected) were generated, with 95% CIs.
  
  
  RESULTS
  The 6 juvenile arthritis registries provided a total of 5294 patients. The mean age at cohort entry was 8.9 (SD 5.0) years and 68% of participants were female. The mean duration of follow-up was 6.8 years with a total of 36 063 person-years spanning 1978-2012. During follow-up, 9 invasive cancers occurred, compared with 10.9 expected (SIR 0.82, 95% CI 0.38 to 1.5). 3 of these were haematological (Hodgkin's, non-Hodgkin's lymphoma and leukaemia). 6 of the patients with cancer were exposed to disease-modifying drugs; 5 of these had also been exposed to biological agents.
  
  
  CONCLUSIONS
  We did not clearly demonstrate an increase in overall malignancy risk in patients with juvenile-onset arthritis followed for an average of almost 7 years. 3 of the 9 observed cancers were haematological. 5 of the cancers arose in children exposed to biological agents. Longer follow-up of this population is warranted, with further study of drug effects.
authors.affiliation: Department of Medicine , McGill University , Montreal, Quebec , Canada.
authors.forename: Omid
authors.initials: O
authors.lastname: Zahedi Niaki
authors.affiliation: Department of Medicine , University of Calgary , Calgary, Alberta , Canada.
authors.forename: Ann E
authors.initials: AE
authors.lastname: Clarke
authors.affiliation: Northwestern University, Feinberg School of Medicine , Chicago, Illinois , USA.
authors.forename: Rosalind
authors.initials: R
authors.lastname: Ramsey-Goldman
authors.affiliation: Division of Rheumatology , The Hospital for Sick Children , Toronto, Ontario , Canada.
authors.forename: Rae
authors.initials: R
authors.lastname: Yeung
authors.affiliation: Department of Rheumatology , Seattle Children's Hospital , Seattle, Washington , USA.
authors.forename: Kristen
authors.initials: K
authors.lastname: Hayward
authors.affiliation: Department of Pediatrics , University of Manitoba , Winnipeg, Manitoba , Canada.
authors.forename: Kiem
authors.initials: K
authors.lastname: Oen
authors.affiliation: Department of Pediatrics , Children's Hospital of Eastern Ontario , Ottawa, Ontario , Canada.
authors.forename: Ciarán M
authors.initials: CM
authors.lastname: Duffy
authors.affiliation: Department of Pediatrics , Royal University Hospital , Saskatoon, Saskatchewan , Canada.
authors.forename: Alan
authors.initials: A
authors.lastname: Rosenberg
authors.affiliation: Division of Pediatric Rheumatology , Riley Hospital for Children , Indianapolis, Indiana , USA.
authors.forename: Kathleen M
authors.initials: KM
authors.lastname: O'Neil
authors.affiliation: Department of Pediatric Rheum San Francisco , University of California , San Francisco, California , USA.
authors.forename: Emily
authors.initials: E
authors.lastname: von Scheven
authors.affiliation: Department of Pediatrics , Duke University Medical Center , Durham, North Carolina , USA.
authors.forename: Laura
authors.initials: L
authors.lastname: Schanberg
authors.affiliation: Department of Medicine , McGill University , Montreal, Quebec , Canada.
authors.forename: Jeremy
authors.initials: J
authors.lastname: Labrecque
authors.affiliation: Division of Rheumatology , The Hospital for Sick Children , Toronto, Ontario , Canada.
authors.forename: Shirley M L
authors.initials: SM
authors.lastname: Tse
authors.affiliation: Division of Rheumatology , The Hospital for Sick Children , Toronto, Ontario , Canada.
authors.forename: Rachana
authors.initials: R
authors.lastname: Hasija
authors.affiliation: Department of Medicine , McGill University , Montreal, Quebec , Canada.
authors.forename: Jennifer L F
authors.initials: JL
authors.lastname: Lee
authors.affiliation: Department of Medicine, McGill University, Montreal, Quebec, Canada; Division of Clinical Epidemiology, Research Institute of the McGill University Health Centre, Montreal, Quebec, Canada.
authors.forename: Sasha
authors.initials: S
authors.lastname: Bernatsky
keywords: Arthritis; Epidemiology; Juvenile Idiopathic Arthritis