18F-FDG PET-CT scanning and diabetic patients: what to do?

PET with computed tomography (PET-CT) is an important imaging modality in the assessment of patients with cancer. The glucose analogue fluorine-18 2'-fluorodeoxyglucose (F-FDG) is a commonly used tracer in PET-CT. As we serve a diverse population with a high prevalence of diabetes mellitus (DM) and malignant disease, we wished to ensure that patients had access to the PET-CT imaging service as efficiently as possible.

We reviewed the simple instructions followed by patients and technical staff in preparation for F-FDG PET-CT scanning at our institution to ensure that there was minimum disruption to the diagnostic pathway.

Only a small percentage (1.5%, 3/200) of patients referred for PET-CT could not proceed with scanning because of unacceptably high serum glucose (SG) levels at the first attendance (SG≥11.1 mmol/l), all of whom were successfully scanned within a week. This cutoff level of SG is based on the European Association of Nuclear Medicine (EANM) guidelines. There was no case in which the patient's diagnostic pathway was delayed purely by the time taken to control glycaemic levels. A significant number of patients were in fact diagnosed with DM, impaired glucose tolerance or impaired fasting glucose as a result of being referred for the PET-CT scan. These patients were actually those for whom a diagnosis of DM was thought to be absent at the time of referral, as opposed to those for whom the diagnosis was not known one way or the other.

We conclude that scheduling for F-FDG PET-CT can be performed efficiently using simple preparation instructions, even in the context of high prevalence of DM and with a high rate of incidental diagnosis of DM at the time of scanning.