BERLIN – Nonmelanoma skin cancer was the only type of malignancy found to occur at an increased rate in new 5-year follow-up data on 535 patients treated for systemic small-vessel vasculitis in four major randomized trials sponsored by the European Vasculitis Society.
With 2,650 person-years of prospective observation of 281 clinical trial participants treated for granulomatosis with polyangiitis (formerly called Wegener’s granulomatosis) and 254 treated for microscopic polyangiitis, patients with circulating antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis had a 2.78-fold greater incidence of nonmelanoma skin cancer than did the matched general population, based upon data from the European cancer registry. But no other type of cancer was significantly increased, Dr. Kerstin W.A. Westman reported at the annual European Congress of Rheumatology.
This finding came as a pleasant surprise. Earlier publications by other investigators have reported broadly elevated malignancy risks in the years following administration of the various toxic, largely cyclophosphamide-based therapeutic regimens for ANCA-associated vasculitis, noted Dr. Westman, a nephrologist at Lund (Sweden) University.
For example, Danish investigators reported significantly increased rates of bladder and prostate cancer and acute myeloid leukemia as well as nonmelanoma skin cancer in a study featuring 2,121 person-years of follow-up (J. Rheumatol.2008;35:100-5). However, the Danish patients were treated during 1973-1999, while participants in the four European Vasculitis Society randomized trials underwent treatment as recently as 2007, at which time, the research focus had shifted to trying to decrease the burden of immunosuppression while maintaining effectiveness, Dr. Westman observed. For this reason, she and her coworkers are cautiously optimistic about the limited cancer risk seen to date in their analysis.
"This may be caused by too short a period of time of follow-up or else, as we would like to think, maybe we have improved the treatment by lowering the cumulative dose of cyclophosphamide, making it less toxic. But that we don’t really know yet," she said.
Several audience members rose to relate that their own clinical experience has been that lymphoma, bladder cancer, and other malignancies crop up not within 5 years post treatment for ANCA-associated vasculitis, but 10-15 years later or even more.
"I completely agree," Dr. Westman replied. "It’s important for us to arrange longer-term follow-up to say anything conclusive about malignancy. We’re aiming for 10-year follow-up in these patients."
Still, she added, there is reason to be hopeful that some of the more recently evaluated treatment regimens are less oncogenic. For one thing, the earlier Danish study found increased rates of several types of cancer within 5 years.
Also, she cited a recent report on 445 patients with granulomatosis with polyangiitis treated during the past 4 decades at a single large German academic rheumatology center. The German investigators found no increase in malignancies. Moreover, the standardized mortality ratio – essentially, the risk of all-cause mortality compared to that of the matched general population – fell from 2.1 in patients treated during 1966-1993, to 1.41 in those treated in 1994-1998, to 1.03, meaning no increased risk, in patients treated in 1999-2002. Relapse rates during those three time periods dropped from 61% to 51% to 35% (Arthritis Rheum. 2011;63:257-66).
The four-study European Vasculitis Society cohort followed prospectively for 5 years had a median age of 61 years at the time of enrollment in the randomized trials. Of the 535 patients, 53% had antiproteinase-3 antibody positive ANCA (PR3-ANCA) and 38% had antimyeloperoxidase-positive ANCA.
Overall survival at 2 and 5 years was 85% and 78%, respectively. Mortality was 2.6-fold higher than in the age- and sex-matched general population. The mortality risk was greatest during the first year of follow up, with deaths mainly from infection or active vasculitis. After year 1, most deaths were caused by infection, cardiovascular events, or cancer.
Relapse, defined as new or worsened manifestations of ANCA-associated vasculitis requiring a change in therapy, occurred in 38% of patients. The two major risk factors for relapse were being PR3-ANCA positive or having cardiovascular involvement at enrollment.
The best 5-year overall survival was in patients younger than age 50 years at enrollment in their randomized trial. Survival was significantly worse in stepwise fashion in 50- to 60-year-olds, worse yet in 60- to 70-year-olds, and lowest of all in patients above age 70 years.
"Age matters," Dr. Westman declared.
One or more cardiovascular events occurred in 14% of the subjects during 5 years of follow-up. There were 32 cardiovascular deaths, 25 nonfatal strokes, and 42 nonfatal myocardial infarctions or revascularization procedures. Not surprisingly, older age was an independent risk factor for cardiovascular events. But PR3-ANCA–positive status proved to be an independent protector against cardiovascular events; it was associated with a 59% reduction in risk.