Optimization of the discontinuation of metformin in diabetic patients explored with ¹⁸F-FDG PET/CT

Objectives To determine if in patients with type 2 diabetes mellitus (T2D), 24 or 48 h of metformin (M) discontinuation could be useful to reduce FDG intestinal uptake keeping patient's glucose level (GL) in normal range and improving PET/CT quality (1,2).

Methods Ninety-one T2D patients treated with antidiabetic drugs (AD) were included. AD regimen included metformin in 72 (group A) and other AD in 19 (group B). 20 patients without T2D served as controls (group C). Group A was divided in 3 subgroups: 30 patients (group A1) were taking M, 21 (group A2) were asked to discontinue M for 24 h before PET/CT and the remaining 21 (group A3) to discontinue M for 48 h. The intestinal FDG uptake was assessed qualitatively (normal, mild, moderate or intense) and semi-quantitatively using SUVmax, SUVmean, SUVpeak values and tissue-to-background ratio (TBR). Results were compared among groups.

Results Intense intestinal uptake in group A3 (9,5%) was lower than in A2 (48%) and A1 (77%) and comparable to B (16%) and C (10%). Intestinal FDG uptake in group A was reduced after M discontinuation for 24 h (TBR A1=1,77 vs TBR A2=1,48; p=ns) and significantly after 48 h (TBR A3=1,10; p<0.001). There were no significant differences among groups A3 (TBR=1,72), B (TBR=1,65) and C (TBR=1,51). There were no statistical differences in age and body mass index (BMI) among groups. GL was higher in group A (123±21) than in B (118±18) and C (93±11) (p<0, 01).

Conclusions AD discontinuation for 48 h is feasible and better than 24 h for reducing intestinal FDG uptake in T2D and it significantly improves PET/CT studies quality. Although GL increased with discontinuation, they were in normal range according to the guidelines.