Evidence for uncoupling of clinical and 18-FDG activity of PET/CT scan improvement in tocilizumab-treated patients with large-vessel giant cell arteritis

Abstract

Objective. Clinical improvement following tocilizumab (TCZ) therapy in patients with large-vessel (LVV) giant cell arteritis (GCA) is well established. However, information on TCZ effect on imaging vascular activity is limited. We aimed to determine if clinical improvement correlated with reduction of vascular 18 F-fluorodeoxyglucose ( 18 F-FDG) uptake in positron emission tomography (PET/CT) scans. Methods. Observational study of patients with refractory LVV-GCA treated with TCZ who had a baseline and a follow-up 18 F-FDG-PET/CT scan. For the visual analysis of 18 F-FDG vascular uptake, a total vascular score (TVS) was defined, ranging from 0 to 15. Besides, a semiquantitative analysis was performed as a target to background ratio (TBR)= SUVmax thoracic aorta wall/SUVmax aortic vascular pool. The baseline and follow-up TVS and TBR were compared. Clinical and laboratory outcomes were also assessed. Results. We included 30 patients (24 women/6 men); mean age±standard deviation 65.7±9.8 years. Baseline PET/CT scans were performed due to active disease at a median [interquartile range-IQR] of 1.5 [0.0-4.0] months before TCZ onset. Following TCZ therapy, 25 (83.33%) patients achieved clinical remission and reduction of 18 F-FDG vascular uptake was also observed after a mean ± standard deviation of 10.8±3.7 months. TBR decreased from 1.70 ± 0.52 to 1.48 ± 0.25 (p=0.005) and TVS from 4.97±2.62 to 3.13±1.89 (p< 0.001). However, only 9 (30.0%) patients showed complete normalisation of TBR and only 3 (10%) normalisation of TVS. TBR and TVS showed a good correlation (r=0.576). Conclusion.Although most LVV-GCA patients achieve clinical remission after TCZ therapy, less than one-third show normalisation of 18 F-FDG vascular uptake.

The role of PET/CT in disease activity assessment in patients with large vessel vasculitis

“…However, persistence of FDG vascular uptake is frequently observed in patients with LVV, even in those treated with anti-IL-6 therapy [ 15 ]. In this regard, a recent study on 30 tocilizumab-treated patients with LVV who underwent PET/CT scans due to active disease before tocilizumab use showed that although most of them achieved clinical remission following therapy, less than one-third showed normalization of FDG vascular uptake [ 26 ].…”

Tocilizumab in refractory Caucasian Takayasu’s arteritis: a multicenter study of 54 patients and literature review

“…These findings suggest that a discordance between clinical and imaging activity assessment may exist, as it has been observed in patients with large-vessel giant cell arteritis treated with TCZ. 25 The assessment of disease activity in TAK remains a challenge, particularly in patients undergoing TCZ therapy in whom acute phase reactants levels are not reliable indicators of relapse. Vascular progression has been reported on imaging techniques despite clinical remission and normal acute phase reactants.…”

“…Vascular progression has been reported on imaging techniques despite clinical remission and normal acute phase reactants. 25–28…”

Immunosuppressive Therapy in Giant Cell Arteritis: Do Steroids Still Reign Supreme?

“…an indication of vascular inflammation) in positron emission tomography-computed tomography scans. 70 Furthermore, the benchmark RCTs only investigated the effect of tocilizumab on GCA when it was used in conjunction with corticosteroids, not when it was used in isolation.…”