Metformin Discontinuation prior to FDG PET/CT: A Randomized Controlled Study to Compare 24- and 48-hour Bowel Activity

Abstract

Purpose To investigate the relationship of 24- and 48-hour metformin discontinuation to bowel uptake of fluorine 18 fluorodeoxyglucose (FDG) on PET/CT scans. Materials and Methods Patients with diabetes who were treated with metformin and referred for FDG PET/CT were randomized to three equal groups based on duration of metformin discontinuation: 24 hours, 48 hours, and no discontinuation (control group). Two interpreters blinded to the study groups assessed FDG uptake in multiple segments of small and large bowel qualitatively and semiquantitatively by using maximum standardized uptake values (SUVs). Differences in age, sex, weight, dose of metformin, duration of metformin treatment, blood glucose levels, and FDG dose injected were assessed. Data were analyzed with analysis of variance when passing normality, and by nonparametric testing when not. Results Ninety study participants (62 male, 28 female; median age, 70 years) were enrolled from July 2010 through March 2012. There were no differences between study groups in weight, blood glucose levels 3 days prior to scanning, or normal organ uptake. Large bowel SUV was lower after 24 hours (4.10 ± 2.00 vs 5.42 ± 2.36; P = .020) and 48 hours (2.63 ± 0.88 vs 5.42 ± 2.36; P ˂ .001) of metformin discontinuation than for no discontinuation (control), and for 48 hours versus 24 hours of discontinuation (P = .0015). Small bowel SUV was lower after 24 hours (2.86 ± 0.67 vs 3.73 ± 1.08 [control]; P ˂ .001) and 48 hours (2.78 ± 0.73 vs 3.73 ± 1.08 [control]; P ˂ .001) of metformin discontinuation versus no metformin discontinuation, but not for 48 hours versus 24 hours of discontinuation (P = .57). Examination-day blood glucose levels increased after 48-hour withdrawal of metformin (8.41 mmol/L ± 2.86 vs 6.83 mmol/L ± 2.13 [control]; P = .002). Conclusion Metformin discontinuation for 48 hours prior to PET/CT was associated with lower accumulation of fluorodeoxyglucose in the bowel, compared to when there was no discontinuation (control group) or 24-hour discontinuation of metformin. © RSNA, 2018.

Discontinuation of metformin to prevent metformin-induced high colonic FDG uptake: is 48 h sufficient?

“…In our study, performed in a European population, we included more patients discontinuing metformin for at least 48 h (n = 25), this contributes evidence to the theory that a metformin discontinuation period of 48 h is insufficient to prevent FDG uptake in all of the colonic segments. Our results contradict the results found in a study by Hamidizadeh et al which showed that a discontinuation period of 48 h lowered the FDG uptake in all of the colonic segments [8]. In our study, we used a different control group in comparison with the studies of Lee et al and Hamidizadeh et al [8,9].…”

“…The Society of Nuclear Medicine and Molecular Imaging (SNMMI) does not specify guidelines for PET procedures made in patients on oral antidiabetics [7]. However, several studies have suggested that metformin should be discontinued prior to the FDG PET scan [2][3][4], and have recommended feasible and optimal discontinuation periods of metformin [4,8,9] to limit the amount of FDG uptake. Even so, the results in these studies are contradictory.…”

“…Even so, the results in these studies are contradictory. Studies by Oh et al and Hamidizadeh et al found that discontinuing metformin for 48 h reduced the intestinal FDG uptake in comparison to the group that continued metformin [4,8]. Oh et al concluded that discontinuing metformin 48 h before an FDG PET scan is an effective preparation [4].…”

The utility of pharmacological and radiological interventions to optimize diagnostic information from PET/CT

“…In a prospective randomized single centre trial comparing the effects of a 24H- and 48H metformin discontinuation, Hamidizadeh and colleagues [ 33 ] provided solid evidence to support a 48H metformin discontinuation prior to FDG PET scan, with limited impact on glycaemia.…”

To Hold or Not to Hold Metformin for FDG PET Scans: That Is the Question

“…Beyond case examples, we also need data to support the degree to which this protocol improves the sensitivity or the confidence of readers to diagnose FDG-avid abdominopelvic malignancies. case for withholding metformin for 48 hours prior to FDG PET scans (3). A total of 90 study participants with diabetes were randomly separated into three equal cohorts of 30; metformin was discontinued at 24 hours or 48 hours prior to FDG PET/CT scans, and a control cohort of study participants with diabetes continued on metformin.…”