Risk for malignant lymphoma in ankylosing spondylitis. a nationwide swedish case-control study

Johan Askling ^1*, Lars Klareskog ², Michael Fored ¹, Paul Blomqvist ¹ and Nils Feltelius ¹

¹ Karolinska Institutet, Sweden
² Karolinska Hospital, Sweden

^* To whom correspondence should be addressed. E-mail: johan.askling{at}medks.ki.se.

Accepted 9 January 2006

Abstract

BACKGROUND: Several inflammatory conditions are associated with increased lymphoma risks. Which specific features of inflammation that mediates this risk is unknown. Whether Ankylosing Spondylitis (AS) increases lymphoma risk is little studied. Besides inflammation- lymphoma etiology, information on lymphoma risk in AS is particularly important as benchmark in the safety evaluation of e.g., TNF-inhibitors.

METHODS: We assessed the association between AS and malignant lymphomas (overall, and separately for NHL, HL, and CLL) in a nationwide, population-based case- control study of 50,615 lymphoma cases and 92,928 matched population-controls using prospectively recorded data on lymphomas from the Swedish Cancer Register 1964- 2000 and data on pre-lymphoma hospitalisations for AS from the Swedish Inpatient Register 1964-2000. We calculated odds ratios (OR) associated with a pre- lymphoma hospitalisation for AS using conditional logistic regression.

RESULTS: 23 (0.05%) lymphoma cases and 41 (0.05%) controls had a pre-lymphoma hospitalization listing AS, relative risk=1.0 (95% CI 0.6-1.7). The number of discharges, and the mean latency between AS and lymphoma, were similar among cases and controls. Analyses restricted to lymphomas diagnosed during the 1990s revealed similar results (OR=1.3, 95% CI 0.6-2.5, n exposed cases/controls=14/21).

CONCLUSIONS: On average and in the absence of TNF- inhibitors, hospitalised AS does not appreciably increase lymphoma risk.

Keywords: Sweden, ankylosing spondylitis, case-control, malignant lymphoma, register

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