To investigate the incidence of malignancies during longitudinal followup of patients with antineutrophil cytoplasmic antibody-associated vasculitis (AAV), and to examine the effect of immunosuppressive therapy on malignancy risk in these patients.
The study population consisted of patients with histopathologically confirmed AAV, diagnosed between 1991 and 2013 at a large university hospital. The mean duration of followup was 10 years. Malignancy incidence was assessed using the Dutch National Pathology Database. Incidence rates from the Netherlands Cancer Registry were used to compare malignancy incidence in the AAV cohort to that in the general Dutch population.
Thirty-six of 138 patients with AAV developed a total of 85 malignancies during a mean followup of 9.7 years. The sex-, age-, and calendar year-adjusted malignancy risk was 2.21-fold higher (95% confidence interval [95% CI] 1.64-2.92) than that in the general population. Non-melanoma skin cancers occurred most frequently (standardized incidence ratio 4.23 [95% CI 2.76-6.19]). The incidence rates of other malignancies were not significantly increased. Malignancy risk was associated with the duration of cyclophosphamide (CYC) therapy and, interestingly, was not increased in patients who had received CYC for <1 year.
Patients with AAV have a higher risk of malignancy than the general population, but this risk is accounted for solely by non-melanoma skin cancers. Over the years, the risk of other malignancies-specifically bladder and hematologic malignancies-has decreased in patients with AAV. This finding reflects ongoing efforts to reduce CYC exposure by developing new treatment regimens.