18F-FDG Muscular Uptake in Statin-Associated Symptoms Without Myositis: How Long to Stop Treatment for Image Quality Improvement?

Statin-associated muscle symptoms (SAMSs) are a frequent adverse effect of statin treatment (7%–29%) and the main reason for nonadherence.1 SAMS can occur with normal or slightly elevated serum creatine kinase (CK). The etiology is complex with multifactorial mechanisms and appears more frequently in women.2 Myopathy is a rarer complication with muscular inflammation and increased CK. Diffuse 18F-FDG muscular uptake on PET was reported in statin-related rhabdomyolysis3,4 and other myopathies.5–7 In men, but not in women, the risk of statin-related myopathy is dose-dependent.2 In this case, a 80-year-old man was referred for 18F-FDG PET in hemopathy follow-up. A long-term statin treatment was prescribed for cardiovascular prevention. On examination, the patient described mild chronic myalgia for more than 6 months. CK and C-reactive protein were normal. Clinically, the patient was classified statin-related myotoxicity (SRM) 1 on the 7-point SRM scale. Acquisitions were all obtained on PET/CT (Biograph mCT Flow; Siemens) 60 minutes after 3.5 MBq/kg 18F-FDG injection. Table flow acquisition was 1.3 mm/s. The patient was fasting without any treatment for at least 6 hours, and glycemia was controlled and normal (5.4–7.0 mmol/L). Reference PET acquisition (A) showed an abnormal diffuse 18F-FDG muscular uptake on MIP, more pronounced on shoulders, arms, hips, legs, and feet. This aspect remained similar on the second examination without treatment for 6 hours (B). On the follow-up with a statin discontinuation for 3 days (C) and 7 days (D), an image quality improvement was observed with less muscular uptake and a better 18F-FDG bioavailability, especially on brain. The 1-week statin-free medication showed a better overall image quality except arm movements during the acquisition. Cervical hypermetabolisms were related to uptakes in contracting skeletal muscles. On pelvic transaxial fused PET/CT slices (below MIP images), there was an hypermetabolism of gluteal muscles, which was gradually reduced after 7 days of statin discontinuation. The 2 last acquisitions also revealed osseous and pulmonary focal uptakes related to hemopathy. Diffuse muscular uptake has been reported to alter the tumoral contrast and PET lesion detectability.8 This case illustrates the possibility of diffuse muscular FDG uptake in SAMS without biological myositis and the need for a minimal 1-week statin discontinuation to improve image quality. This treatment interruption could be planned as the first biological modifications described in the literature were observed from a 5-day statin interruption9 with only impact on long-term cardiovascular risks after a 3-month discontinuation.10–12 Thus, this short statin discontinuation could be conceivable without impact on the patient cardiovascular risk. A study on a larger cohort would allow a better assessment of an ideal discontinuation time.

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