Background/Purpose:

 Management of PMR and GCA can be challenging in patients with persistently elevated inflammatory markers, prominent constitutional symptoms and inadequate steroid response. We undertook an audit in such difficult to treat cases of the utility of FDG-PET CT scanning and outcomes of therapeutic decisions subsequently made.

Methods:  We report a retrospective case notes review of 52 rheumatology patients with active PMR, GCA despite optimal steroid/ methotrexate therapy or patients with an unexplained systemic illness who had PET-CT from 2008–2012.  FDG uptake was graded on a 4-point scale and grade 2 or more was accepted as positive.

Results: Of the 52, 68 % were female (median age 70, range 57–89), 23 PMR and 20 had GCA (12  biopsy positive). 63 % PMR and GCA patients were on steroids. The average dose of Prednisolone prior to PET scan was 6mg daily in PET positives compared to 21mg daily in PET negative patients.

 Large vessel vasculitis (LVV): 15 had avid FDG uptake in the subclavian, aortic and axillary arteries, suggesting presence of LVV. All had constitutional symptoms notably night sweats, weight loss and lethargy. The average CRP in patients with LVV was 112mg/dl (range 13-403). Where PET scans were negative, the average CRP was 19 (1-48). There was no significant difference in gender, incidence of PMR, GCA, and resistance to treatment in both groups. 8 out of 9 with LVV who had abdominal CT scan were found to have inflammatory aortitis (soft tissue vascular cuffing) on retrospective CT review. All patients with LVV had successful clinical response to escalation of immunosuppression with 4-6 weeks post treatment mean CRP of 7 (1-26). 78% were treated with high dose Predinisolone and Leflunomide (53%). 4 patients required treatment with Tocilizumab (TCZ). 1 patient with retroperitoneal fibrosis and LVV associated with pan aortitis was treated with Rituximab. All patients on TCZ showed reversal of FDG avidity, normalized CRP, reduction of prednisolone to < 90% pre TCZ dose and 1 showed re-vascularisation of axillary artery stenosis on follow up CT angiography and ultrasound. 

Non LVV findings on FDG PET: 2 patients had uptake in sterno-clavicular and sacroiliac joints suggestive of SpA. One patient with connective tissue disease overlap had symmetrical uptake in shoulders consistent with inflammatory arthritis. In 2 patients with atypical clinical presentation the diagnosis of PMR was confirmed with bursal & entheseal uptake in the shoulder/hips. In 3 cases FDG PET revealed cancer (pancreas 2, metastatic breast 1).

Conclusion:  LVV is a common finding in both PMR and GCA exhibiting lack of steroid response, constitutional symptoms and raised inflammatory markers. Abdominal CT scan may provide important diagnostic clues of aortitis which can be confirmed on FDG-PET scan. Scan results are influenced by dose of steroid intake and we suggest prednisolone no higher than 7.5 -10mg daily a week prior to the scan. Patients on higher doses may have false negative scans. FDG PET can also reveal occult malignancies or confirm the PMR diagnosis.  Novel agents like leflunomide and tocilizumab provide targeted and effective therapy in refractory patients with reversal of FDG avidity on and re-vascularisation on repeat scans.

ACR Meeting Abstracts - https://acrabstracts.org/abstract/prevalence-management-and-outcomes-of-pet-positive-large-vessel-vasculitis-in-difficult-to-treat-pmr-and-gca-patients/