ANCA vasculitis is a significant challenge that faces all rheumatologists. Two of the major issues include disease flare after remission and long-term therapeutic toxicity.
We know from the RAVE trial that rituximab (RTX) is as effective as cyclophosphamide (CYC) to achieve a primary outcome of remission at 6 months with no steroids. The RAVE trial also showed that RTX was superior to CYC in prior relapsers. However, longer-term follow-up of the RAVE participants at 18 months showed a relapse rate of 50-60%, which is much too high.
The MAINRITSAN trial set out to study longer-term outcomes of ANCA vasculitis patients. It is important to know how this study was done. Patients received induction therapy with CYC and steroids and were in remission at 6 months. They were then randomized to receive AZA oral daily or RTX infusions at day 0, 15, and month 6, 12, and 18. Note that the last dose of RTX was at month 18. The initial primary endpoint was the proportion of patients relapsing at month 28. RTX was superior to AZA in maintaining remission.
Today at the ACR meeting, the 60-month (5-year) follow-up data were presented. Of the 115 original patients enrolled, 96% remained and completed follow-up at 60 months.
Rate of Relapse
The rate of major relapse was 28% in the RTX group vs 50% in the AZA group. The rate of major and minor relapses combined was 42% in the RTX group and 62% in the AZA group.
There were no deaths in the RTX group. There were 4 deaths in the AZA group.
Serious Adverse Events
SAE's were slightly increased in the RTX arm mainly due to bronchitis and pneumonia. The rates of cardiovascular events were similar in both groups. There were more malignancies in the AZA group mainly due to skin cancer.
Predictive Factor for Flare
There were two factors that could be used to predict a flare:
Positive ANCA level at month 12
Patients who were both PR3-ANCA positive and had detectable ANCA levels at 12 months were at the highest risk of flare.
The maintenance of disease control in ANCA vasculitis is incredibly challenging. I view it like weight loss: it's easy to take the weight off but hard to keep it off. This is another very reassuring study that shows RTX is superior to AZA in maintaining remission for patients with ANCA vasculitis. What's very interesting is the last dose of RTX was given at month 18 and looking out to 5 years, only 29% relapsed.
I have to say in clinical practice that we would normally give RTX on a more regular basis but it is difficult to know how much is enough and how much is too much. Furthermore, every patient is different. Should we give RTX in small doses every 4 months, or should we give larger doses but less frequently?
I must applaud the vasculitis research groups for doing studies that are actually very impactful clinically. I would now challenge them to consider two things:
What is the most effective dosing regimen for maintenance in patients who require induction therapy?
What do we do in early AAV? Should we be treating these patients with RTX to prevent progression and severe flare?