Background The long-term cancer-risk of patients treated for granulomatosis with polyangiitis (Wegener's; GPA) is not well characterized.

Objectives We assessed the risk of early and late-occurring cancers among 293 patients diagnosed with GPA during 1973-1999 and followed throughout 2010.

Methods The cancer-incidence in the cohort was determined by linkage with the Danish Cancer Registry and compared to that in the general population by calculation of standardized incidence ratios (SIRs).

Results The median duration of follow-up was 9.7 (range: 0-36) years. 73 cancers occurred, of which 30 were non-melanoma skin cancers (NMSC) and 11 were bladder carcinomas. A high occurrence of NMSC was observed from the second year of follow-up onwards, with a SIR of 7.0 (95% CI: 2.3-16) for cases diagnosed ≥20 years after GPA. The incidence of bladder cancer was increased after 5-9, 10-14, and 15-19 years of follow-up, with SIR estimates for these latency-periods of 5.3 (95% CI: 1.1-15), 14.4 (95% CI: 5.3-31), and 10.5 (95% CI: 1.2-38), respectively. The incidence of myeloid leukemia was significantly increased during year 5-9 (SIR: 23.9 (95% CI: 2.7-86)). Increased incidence of NMSC, bladder cancer, and myeloid leukemia was observed among patients exposed to cumulative cyclophosphamide-doses >36 gram, while the only malignancy-type observed in excess among those treated with lower cyclophosphamide-doses was NMSC. The cancer-risk among cyclophosphamide-naïve patients was not significantly increased.

Conclusions GPA patients experience a greater-than-expected number of cancers following conventional therapies, including an increased number of very late-occurring malignancies. The risk of specific cancer-types rises with the cumulative cyclophosphamide-dose administered.

Disclosure of Interest None declared

DOI 10.1136/annrheumdis-2014-eular.5439