Effect of rituximab on malignancy risk in patients with ANCA-associated vasculitis.
OBJECTIVES
Patients with antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) treated with cyclophosphamide have an increased malignancy risk compared with the general population. We investigated whether treatment with rituximab instead of cyclophosphamide has decreased the malignancy risk in patients with AAV.


METHODS
The study included patients with AAV treated at a tertiary vasculitis referral centre between 2000 and 2014. The malignancy incidence in these patients was compared with the incidence in the general population by calculating standardised incidence ratios (SIRs), adjusted for sex, age and calendar year. Malignancy incidence was compared between rituximab-treated and cyclophosphamide-treated patients.


RESULTS
Of the 323 included patients, 33 developed a total of 45 malignancies during a mean follow-up of 5.6 years. This represented a 1.89-fold increased (95% CI 1.38 to 2.53) malignancy risk, and a non-significantly increased risk if non-melanoma skin cancer was excluded (SIR, 1.09; 95% CI 0.67 to 1.69). The risk of non-melanoma skin cancer was 4.58-fold increased (95% CI 2.96 to 6.76). Cyclophosphamide-treated patients had an increased malignancy risk compared with the general population (SIR, 3.10; 95% CI 2.06 to 4.48). In contrast, rituximab-treated patients had a malignancy risk similar to the general population (SIR, 0.67; 95% CI 0.08 to 2.43). The malignancy risk in cyclophosphamide-treated patients was 4.61-fold higher (95% CI 1.16 to 39.98) than in rituximab-treated patients.


CONCLUSIONS
The malignancy risk in patients with AAV was lower in rituximab-treated patients than in cyclophosphamide-treated patients. Notably, rituximab treatment was not associated with an increased malignancy risk compared with the general population. Rituximab could therefore be a safe alternative to cyclophosphamide in the treatment of AAV.
['van Daalen|Emma E|EE|', 'Rizzo|Raffaella|R|', 'Kronbichler|Andreas|A|', 'Wolterbeek|Ron|R|', 'Bruijn|Jan A|JA|', 'Jayne|David R|DR|', 'Bajema|Ingeborg M|IM|', 'Rahmattulla|Chinar|C|']
D000328:Adult D000368:Aged D056648:Anti-Neutrophil Cytoplasmic Antibody-Associated Vasculitis D018501:Antirheumatic Agents D002280:Carcinoma, Basal Cell D002294:Carcinoma, Squamous Cell D003520:Cyclophosphamide D004305:Dose-Response Relationship, Drug D005260:Female D005500:Follow-Up Studies D006801:Humans D015994:Incidence D008297:Male D008875:Middle Aged D009369:Neoplasms D000069283:Rituximab D012878:Skin Neoplasms
Cyclophosphamide DMARDs (biologic) Outcomes research Systemic vasculitis