Cancer incidence in a population‐based cohort of patients with Wegener's granulomatosis

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Abstract
Wegener's granulomatosis is necrotizing granulomatous vasculitis of unknown origin, which untreated has a high mortality within the first year of onset. The introduction of corticosteroids and cyclophosphamide in the treatment has considerably improved survival rates, but past studies have indicated an increased cancer risk, including an increased risk for urinary bladder cancer. No large assessment of the general cancer occurrence in Wegener's granulomatosis has been reported. The aim of our study was to assess the general incidence of cancer in patients with Wegener's granulomatosis and to put this in relation to the risk for bladder cancer. We identified a population‐based cohort of 1,065 patients with Wegener's granulomatosis in the Swedish In‐patient Register. Through linkage with the Swedish Cancer Register, we followed the cohort for cancer occurrence for up to 26 years. Standardized incidence ratios (SIR) between observed and expected numbers of cancers were used as a measure of relative risk. There was a 2‐fold overall increased risk for cancer in the cohort. The increase was most pronounced for bladder cancer (SIR = 4.8; 95% CI 2.6–8.1), squamous cell skin cancer (SIR = 7.3; 95% CI 4.4–12), leukemias (SIR = 5.7; 95% CI 2.3–12) and for malignant lymphomas (SIR = 4.2; 95% CI 4.2–8.3). The results confirm previous indications of an increased risk for cancer of the urinary bladder but also points to increased risks for cancer at other sites.