Management of hyperglycemia in oncological patients scheduled for an FDG-PET/CT examination

Abstract

Positron-emission tomography combined with X-ray computed tomography and using [18F]-fluorodeoxyglucose (FDG-PET/CT) is being used for staging, restaging, followup, and treatment monitoring of several glucose avid tumors. Since FDG and glucose compete for the same transporters and for hexokinase, hyperglycemia may significantly modify the value of the semi-quantitative variables commonly used for estimating the uptake of FDG, including the standardized uptake value (SUV). Therefore, this issue is of particular relevance, when FDG-PET/CT is used in patients with poorly controlled diabetes mellitus. Thus, because of the competition between FDG and glucose, the control of glycemia may be relevant when imaging is being pursued, with the use of SUV, to estimate the degree of malignancy during the staging of the tumor and in particular for the comparison during follow-up and in case of therapy monitoring. Indeed this issue has been considered, since PET with FDG was in the early phase of introduction into clinical practice about 40 years ago. In spite of the acknowledgement of this very relevant issue, demonstrated by a simple PubMed search using the terms “FDG PET” and “blood glucose levels” and “FDG PET” and “hyperglycemia” that allowed to retrieve more than 200 articles, there is only a limited number of papers dealing with the practical procedure to be used in case of hyperglycemia in oncological patients undergoing an FDGPET/CT examination. The aim of this paper is to provide a practical guidance for the management of hyperglycemia, either due to diabetes mellitus or other causes, in oncological patients scheduled for FDG PET/CT, to optimize the preparation for the exam and increase the reliability of the semi-quantitative assessment of FDG uptake in tumor. The Society of Nuclear Medicine and Molecular Imaging (SNMMI) guidelines recommend rescheduling of the scan when glycemia is above 150–200 mg/dL [1]. The European Association of Nuclear Medicine and Molecular Imaging (EANMMI) guidelines suggest that FDG PET/CT study should be rescheduled, if glycemia is higher than or equal to 200 mg/dL [2]. Both guidelines suggest that pre-scan hyperglycemia may be reduced by administration of rapid-acting insulin. However, the EANM guidelines consider also the impact of longer acting insulin and recommend specific time intervals for the administration of the different types of insulin prior to scan. The inconsistency between different guidelines, which originates from lack of robust and credible evidence, has resulted in a diverse range of accepted pre-scan glycemia levels in clinical PET imaging. In a web-based survey of PET/CT users, specialists from 128 PET centers worldwide responded to the question regarding the pre-scan glycemia cutoff used at their institutes [3]. Cutoff values varied from 150 to 250 mg/dL (8.3–13.9 mmol/L) and 7% of the sites used no cutoff. Based on the recent systematic review and meta-analysis by Eskian et al. [4], patients who are still hyperglycemic after at least 4 h of fasting would have significantly lower FDG uptake in the brain and muscles and significantly higher FDG uptake in the liver and mediastinal blood pool in comparison with euglycemic patients. However, pooled findings reported that glycemia levels This paper represents the opinion of the “AIMN-AMD-AIOM Diabetes and Cancer working group” members: Silvia Acquati, Gennaro Clemente, Romano Danesi, Stella D’Oronzo, Laura Evangelista, Daniele Farci, Pietro Ferrari, Marco Gallo, Marisa Giorgini, Valerio Napoli, Gabriella Piscitelli, Antonio Russo, Matteo Salgarello.