Cyclophosphamide for large vessel vasculitis: assessment of response by PET/CT

Glucocorticosteroids (GC) are the standard treatment for large vessel vasculitis, but some patients are refractory. Cyclophosphamide (CYC) has been shown to be effective in autoimmune diseases.

The study consisted of a retrospective analysis of 10 patients with active large vessel arteritis who received pulse CYC after failure of GC or because of organ threatening stenosis. CYC pulse therapy was started with a dose of 750mg/m² body surface every 3 weeks and increased if necessary. Clinical response was assessed by the Birmingham Vasculitis Activity Score (BVAS), the C-reactive protein and the erythrocyte sedimentation rate (ESR). PET/CT was performed at baseline and during treatment to determine disease activity.

The median BVAS at the time of the initial PET/CT was 6.5 (5-13). The median ESR was 42mm/h (6-94mm/h), and the medium CRP was 4.6mg/dl (0.18-11.8mg/dl). All but one patient experienced a complete clinical remission during CYC treatment after a median of 10 cycles. PET/CT confirmed the efficacy of the treatment by normalisation of FDG uptake during therapy. One patient with persisting inflammation was lost to follow-up. One patient experienced a relapse after 21 months. The remaining 8 patients are still in remission with low-dose GC and a maintenance therapy (azathioprine, methotrexate or mycophenolate) after a median follow-up of 45 months.

Pulse cyclophosphamide is effective in patients with large vessel vasculitis resistant to glucocorticosteroids. The high rate of sustained response in our patients suggests that treatment decisions based on clinical parameters combined with PET/CT may have a beneficial effect on the clinical outcome.