Evaluation of the fractional uptake rate (FUR) in 18F-FDG PET/CT to assess tumour metabolic activity

As most tumours have a high glucose consumption, important information on
tumour metabolism can be obtained from PET imaging using 18F-FDG as a
radioactive glucose analogue. From literature it is known that quantitative
analysis improves the clinical value of 18F-FDG PET. However, instead of
measuring the true tumour glucose consumption Km, in current clinical practice
the 18F-FDG uptake is measured at a certain time after administration as a
surrogate for Km, the so-called standardized uptake value (SUV). As the SUV
suffers from a number of important shortcomings, discrepancies between Km and
the SUV have been reported which may lead to erroneous conclusions regarding
disease progression based on the SUV.
Alternatively, pharmacokinetic modelling approaches facilitate accurate Km
assessment. Unfortunately, these approaches typically require complex
mathematical modelling, lengthy dynamic PET imaging and/or invasive arterial
blood sampling and are therefore not compatible to current clinical oncologic
18F-FDG PET scanning. However, from these models it can be derived that at late
time points after administration Km can be approximated using a simplified
approach known as the fractional uptake rate (FUR). Our hypothesis is that PET
quantification based on the FUR is feasible in clinical routine and will result
in superior 18F-FDG PET quantification compared to the SUV.

Primary objective: To investigate whether FDG PET quantification using the FUR
is superior compared to the clinically used SUV.

Secondary objectives:
1) To evaluate whether the metabolic tumor activity Km can be accurately
asessed with 18F-FDG PET using the FUR.
2) To investigate the impact of the use of patient-specific versus a (scaled)
population-based input function on the accuracy of Km assessment using the FUR.

This study is a cross-sectional observational study in lung cancer and/or
lymphoma patients that will receive an 18F-FDG PET/CT scan as part of standard
clinical care. In contrast to the clinical protocol in which patients will
receive a static whole-body PET/CT scan following a waiting time of 50-60
minutes after 18F-FDG administration, 18F-FDG administration will be performed
inside the PET/CT scanner after which a dynamic whole-body PET/CT scanning
protocol will be conducted. After the dynamic PET scan, the standard static
whole-body PET/CT scan will be performed for the standard clinical diagnosis.
Consequently, patient examination is not prolonged, nor is patient diagnostics
altered in any way.

During the study three additional blood samples will be taken. Blood sampling
itself can cause bruises. Infections or continued bleeding on the other hand
are very rare. The additional effective dose resulting from the extra low-dose
CT examination is between 1-10 mSv (risk category IIb, ICRP 62 publication),
which is recommended and acceptable for research conducted with oncologic
patients having an intermediate to moderate level of societal benefit.
All PET/CT examinations are performed using a CE-registered clinical PET/CT
system (Discovery MI 5R, GE Healthcare). Furthermore all examinations are
conform the intended purpose of the system. The maximum 50 minute dynamic
whole-body PET/CT examination which is additional to the standard care PET/CT
examination performed 60 minutes after 18F-FDG administration comprises the
same examination as in an earlier study which has been approved of by the
Medical Ethics Committee (see also NL74609.068.20)