Background/Purpose: Almost half of all patients diagnosed with PMR require a protracted duration of glucocorticoid therapy due to relapsing disease.(1) On whole body PET/CT, PMR possesses a distinctive pattern of abnormal ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) uptake, however the prognostic potential of this test is unknown. The aim of this study was to characterise ¹⁸F-FDG uptake on whole body PET/CT and investigate its ability to predict relapsing PMR.

Methods: Steroid-naïve patients with newly diagnosed PMR (2012 EULAR/ACR Classification Criteria) were prospectively recruited. Participants with GCA were excluded. Disease activity (PMR-Activity Score [PMR-AS]) was assessed and whole body PET/CT including dedicated hand views undertaken prior to the commencement of a standardised weaning course of prednisolone (BSR Guideline). PMR-AS was recalculated at weeks 4, 8, 16, 24, 32 and 46. Relapse was defined by a PMR-AS score of ≥9.35 in a patient who had achieved clinical remission (PMR-AS < 9.35) or an increase in PMR-AS by ≥6.6 if the participant had been previously responding to treatment (PMR-AS ≥9.35 but falling between successive visits). Qualitative (Meller score) and semi-quantitative (standardised uptake value maximum [SUVmax]) scoring of 21 musculoskeletal sites on whole body PET/CT was performed by two experienced nuclear medicine physicians, with any difference in opinion resolved by consensus. The Cox proportional-hazards model investigated the relationship between relapse and 18F-FDG uptake, with a p-value < 0.05 representing statistical significance.

Results: 35 patients met the inclusion criteria. Mean age was 69.5±7.15 years and 19/35 (54.3%) were male. Findings on whole body PET/CT are presented in Table 1, with a peri-articular pattern of abnormal ¹⁸F-FDG uptake predominating at the shoulder and hip. A high frequency of knee (79.4%) as well as wrist and/or hand involvement (68.6%) was appreciated, including a novel pattern of volar ¹⁸F-FDG uptake (Figure 1). Longitudinal PMR-AS data was available for 32 participants, 25 (78%) of whom relapsed during follow-up. Figure 2 depicts the statistically significant relationship identified between the presence of volar hand ¹⁸F-FDG uptake and later time to first relapse/no relapse (HR 0.25 [0.09 – 0.71], p=0.004).

Conclusion: A novel pattern of volar ¹⁸F-FDG uptake at the hand was associated with glucocorticoid-responsive disease in a prospective cohort of newly diagnosed PMR patients.

(1) Kremers HM, Reinalda MS, Crowson CS, Zinsmeister AR, Hunder GG, Gabriel SE. Relapse in a population based cohort of patients with polymyalgia rheumatica. J Rheumatol. 2005;32(1):65-73.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/a-volar-pattern-of-18f-fluorodeoxyglucose-uptake-at-the-hand-on-whole-body-pet-ct-predicts-glucocorticoid-responsive-disease-in-polymyalgia-rheumatica/