PARIS — Patients with newly diagnosed antineutrophil cytoplasmic antibody-associated vasculitis do not have an increased rate of underlying malignancies, according to the findings of a large Danish case-control study.
“The overall message of our study is that as a clinician you don't have to screen your patients with newly diagnosed [antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis] for any underlying cancer on a routine basis,” Dr. Mikkel Faurschou said at the annual congress of the European League Against Rheumatism.
“There has been speculation that cancer might somehow trigger the [ANCA-associated vasculitis]. Our conclusion is that we cannot confirm that. We don't believe that [ANCA-associated vasculitis] is sometimes a paraneoplastic condition,” added Dr. Faurschou, a rheumatologist at the National University Hospital, Copenhagen.
He reported on 293 ANCA-associated vasculitis (AAV) patients and 2,930 age- and gender-matched controls. The comprehensive Danish Cancer Registry was used to gather data on the occurrence of cancer before the diagnosis of AAV or prior to the same date among controls.
Twenty-six AAV patients had one or more cancers diagnoses at any site prior to diagnosis of their vasculitis, as did 194 controls prior to their cutoff dates. These rates were statistically similar.
In analyzing specific cancer types, the Danish investigators found that only one type of malignancy—testicular cancer—was significantly more common in AAV patients than in controls. However, although the odds ratio of 6.4 sounds impressive, this amounted to a mere two cases in the AAV group, compared with three cases in controls. Given these small case numbers, coupled with the fact that neither of the cases of testicular cancer in AAV patients occurred within 2 years prior to diagnosis of the vasculitis, it's quite unlikely that the malignancies served as a direct trigger in the pathogenesis of the AAV, Dr. Faurschou explained in an interview.
The only type of malignancy that was detected more commonly within 2 years prior to diagnosis of AAV than in controls was nonmelanoma skin cancer. There were 5 cases in the AAV patients and 12 in controls during this time frame, for an odds ratio of 3.9. The finding suggests the possibility that ANCA-associated vasculitis and nonmelanoma skin cancer share a genetic predisposition is worthy of further investigation. Alternatively, it may be the case that AAV patients are somehow immunologically dysfunctional, since nonmelanoma skin cancer is known to be associated with immunodeficiency, the rheumatologist observed.
An earlier report by investigators at the University of Birmingham (England) concluded the risk of malignancy is increased prior to diagnosis of AAV and that cancer should be considered part of the differential diagnosis in patients presenting with AAV (Rheumatology 2004;43:1532-5).
Moreover, German investigators who found an increased rate of renal cell carcinoma in patients recently diagnosed with ANCA-associated vasculitis recommended routinely looking for internal malignancies in such patients (Ann. Rheum. Dis. 2004;63:1183-5). These two prior reports have caused a stir in rheumatology circles because of their assertion that an extensive and costly work-up using abdominal ultrasound, CT, and other tools to rule out cancer is warranted in AAV patients.