LEUVEN, Belgium—Repetitive 18-fluorodeoxyglucose positron emission tomography (FDG-PET) did not help identify PMR patients who are most at risk for relapse after discontinuation of steroid treatment, but it did reveal inflammation of the processi spinosi of the vertebrae in over half the patients, a novel finding that might help explain the morning stiffness associated with the syndrome, report Daniel Blockmans, MD, and associates at University Hospital, in Leuven, Belgium, in the journal Rheumatology.1 Drs. Blockmans, Vanderschueren, Knockaert, and Bobbaers are with the department of general internal medicine; Drs. De Ceuninck and Mortelmans are with the department of nuclear medicine.

"We do not think that repetitive FDG-PET scans offer any advantage over the traditional follow-up of PMR patients, based on clinical evaluation and periodic determination of sedimentation rate and/or CRP [C-reactive protein] levels." —Daniel Blockmans, MD.
"Vascular and articular FDG uptake decreases during treatment with steroids, but FDG-PET results at the time of diagnosis and during steroid treatment do not predict which patients are at risk for later relapses. Therefore, we do not think that repetitive FDG-PET scans offer any advantage over the traditional follow-up of PMR patients, based on clinical evaluation and periodic determination of sedimentation rate and/or CRP [C-reactive protein] levels," writes lead author Dr. Blockmans.

Repeat FDG-PET used in 35 PMR patients

Dr. Blockmans et al studied 35 patients with isolated PMR using FDG-PET before initiation of steroid treatment. These studies were repeated at 3 months in 22 patients and at 6 months in 9 patients. Scans were scored at seven different vascular areas, and a total vascular score (TVS) of 0 to 21 was calculated. FDG uptake was scored from 0 to 2 in the shoulders, hips, and processi spinosi of the vertebrae.

All patients were treated with 12 mg methylprednisolone/day for 2 weeks, then progressively decreased to 8 mg/day for 4 weeks, 6 mg/day for 6 weeks, 4 mg/day for 7 weeks, and 2 mg/day for 7 weeks. All patients also received calcium and vitamin D to prevent osteoporosis. Relapse was defined as recurrence of clinical symptoms (morning stiffness, proximal girdle pain) and an increase of inflammatory parameters (erythrocyte sedimentation rate (ESR) >40 mm/h and/or CRP >30 mg/L), or a recurrence of symptoms that persisted for 4 weeks, even without an increase in ESR or CRP levels.

The researchers found that vascular FDG uptake was present at baseline in only 11 patients (31%), mainly at the subclavian arteries, and mean TVS was low. They also found baseline FDG uptake in shoulders (94%), in processi spinosi (51%), and in hips (9%). "The intensity of FDG uptake in the large vessels or in the shoulders, hips, or processi spinosi did not correlate with the rate of relapse," Dr. Blockmans reports.

The high dropout rate before the 6-month scan, which was accomplished in only seven patients who relapsed and two who did not relapse, complicates interpretation of this study. In an accompanying editorial corresponding author Michael Schirmer, MD, and colleagues comment, "Unfortunately, the power of the Blockmans' study was limited concerning the prediction of PMR relapses by incomplete follow-up data, as only one-third of the patients enrolled into the study completed the planned three serial FDG-PET scans (type II error). A definite conclusion on the value of FDG-PET is thus not possible. The careful reader observes higher FDG uptake 6 months after baseline in the shoulders, ...hips, ...and processi spinosi...of relapsing patients compared with those without relapse, although differences did not reach statistical significance."2

"What is new, and came to us as a surprise, is a clearly increased FDG uptake in the processi spinosi of the lumbar > dorsal > cervical vertebrae in half of our patients. This involvement may be responsible for the morning stiffness in the backs of PMR patients," Dr. Blockmans writes.

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References

1. Blockmans D, De Ceuninck L, Vanderschueren S, et al. Repetitive 18-fluorodeoxyglucose positron emission tomography in isolated polymyalgia rheumatica: a prospective study in 35 patients. Rheumatology. 2007;46:672-677.
2. Dejaco C, Duftner C, Wipfler E, et al.  18F-Fluorodeoxyglucose positron emission tomography in polymyalgia rheumatica: novel insight into complex pathogenesis but questionable use in predicting relapses (editorial). Rheumatology. 2007;46:559-560.