Impact of intravenous insulin on 18F-FDG PET in diabetic cancer patients.
The aims of this study were to evaluate the effectiveness of a standardized insulin protocol in reducing glycemia, review (18)F-FDG biodistribution with such a protocol, and assess its clinical impact.


METHODS
Sixty-three patients with glycemia greater than 10 mmol/L received insulin doses intravenously according to a standardized protocol. One hundred six consecutive euglycemic patients (<6.2 mmol/L) served as controls. (18)F-FDG biodistribution was evaluated by 2 experienced PET readers on a 5-point visual scale based on muscular uptake. The 63 patients who received insulin were divided into insulin subgroup A, with adequate biodistribution (score 0, 1, or 2) and insulin subgroup B, with altered biodistribution (score 3 or 4). 18F-FDG biodistribution was also evaluated semiquantitatively by standardized uptake value (SUV) measurements over the liver, gluteal muscles, and myocardium. Clinical impact (complications and diagnostic accuracy) was assessed by follow-up.


RESULTS
Glycemia decreased from 13+/-2 to 7+/-2 mmol/L after insulin injection. Images showed significantly more muscular uptake in patients who received insulin than in the control group (scores 1.6+/-1.5 vs. 0.4+/-0.6, P<0.05). Twenty-five percent of insulin patients studied had altered biodistribution (insulin subgroup B). The two most important factors increasing muscular uptake were the time interval between insulin and 18F-FDG injection (mean in insulin subgroup A, 80.2+/-17 min; mean in insulin subgroup B, 65.7+/-10 min; P<0.01) and the glycemia interval decrease after insulin injection (mean in insulin subgroup A, 5.3+/-2.6 mmol/L; mean in insulin subgroup B, 7.6+/-1.8 mmol/L; P<0.01). In insulin subgroup B, mean hepatic SUV was lower (1.3+/-0.4 vs. 2.1+/-0.4, P<0.01) and mean muscular SUV was higher (1.8+/-0.1 vs. 0.9+/-0.01, P<0.01). Of the 63 patients who received insulin, 6 had hypoglycemia, but only 2 were symptomatic. No patient had severe complications causing permanent disability.


CONCLUSIONS
A standardized protocol of intravenous insulin before 18F-FDG injection in diabetic cancer patients was safe and effective in reducing glycemia. Acceptable 18F-FDG biodistribution was obtained in 75% of patients receiving insulin. In addition to visually increased muscular uptake, low hepatic 18F-FDG uptake was a good indicator of altered biodistribution.
Roy
Félix-Nicolas
FN
Department of Nuclear Medicine, Centre Hospitalier de l'Université de Montréal, Montréal, Quebec, Canada.
Beaulieu
Sylvain
S
Boucher
Luc
L
Bourdeau
Isabelle
I
Cohade
Christian
C
D000368:Aged; D001786:Blood Glucose / Q000378:metabolism; D002985:Clinical Protocols; D048909:Diabetes Complications / Q000097:blood / Q000000981:diagnostic imaging* / Q000188:drug therapy*; D005260:Female; D005462:Fluorine Radioisotopes / Q000493:pharmacokinetics; D019788:Fluorodeoxyglucose F18 / Q000493:pharmacokinetics; D006801:Humans; D007275:Injections, Intravenous; D007328:Insulin / Q000008:administration & dosage*; D008297:Male; D008875:Middle Aged; D009369:Neoplasms / Q000150:complications* / Q000000981:diagnostic imaging*; D049268:Positron-Emission Tomography; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics
D001786:Blood Glucose; D005462:Fluorine Radioisotopes; D007328:Insulin; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18