Steroids May Be Associated With Extensive Skeletal Muscle Uptake of ¹⁸F-FDG

Purpose: The possibility of steroid administration inducing the extensive skeletal muscle uptake (ESMU) of FDG in PET scans was investigated.Methods: From 8923 consecutive 18F-FDG PET/CT scans taken at our hospital, 23 scans (15 patients) met adult age and ESMU-positive inclusion criteria. Among the 15 patients, 13 with both ESMU-positive and -negative scans were examined for association with steroid administration.Results: Extensive skeletal muscle uptake was associated with a history of steroid administration (chi(2) test: P = 0.001). Notably, 20 ESMU-positive scans and 11 ESMU-negative scans were significantly different, with 0 to 95 days (median, 18.5 days) and 0 to 708 days (median, 319.0 days) since the last steroid administration, respectively (Mann-Whitney U test, P = 0.003). A significant correlation was observed between mean skeletal muscle SUVmax and the number of days since the last steroid administration (Spearman rank correlation coefficient, rho = -0.501, P = 0.004). Specifically, the degree of ESMU tended to decrease over time, after steroid administration. From multiple regression analysis, the number of days since the last steroid administration was significantly associated with mean SUVmax (P = 0.007), but the blood glucose level was not significant (P = 0.204), revealing that the number of days since the last steroid administration was an independent risk factor. Multicollinearity was low (the variance inflation factor was 1.007 for both the number of days since the last steroid administration and blood glucose levels).Conclusions: Steroid administration within months before PET may be one cause of ESMU.