Does 2-FDG PET Accurately Reflect Quantitative In Vivo Glucose Utilization?

Area of Science:

• Nuclear Medicine
• Biochemistry
• Oncology

Background:

• 2-Deoxy-2-¹⁸F-fluoro-d-glucose (2-FDG) PET is a widely used clinical tool for assessing glucose metabolism in various diseases.
• Quantitative analysis relies on the assumption of a constant lumped constant (LC), representing the proportionality between glucose and 2-FDG metabolism.
• However, 2-FDG primarily reflects glucose transport via facilitated-glucose transporters (GLUTs), potentially overlooking sodium-dependent glucose cotransporters (SGLTs).

Purpose of the Study:

• To highlight potential limitations of 2-FDG PET in accurately quantifying in vivo glucose metabolism.
• To emphasize the variability of the lumped constant (LC) in different physiological and pathological conditions.
• To introduce the potential of novel tracers for a more comprehensive assessment of glucose transport.

Main Methods:

• Review of existing literature on 2-FDG PET and glucose transporter mechanisms.
• Discussion of the implications of SGLT-mediated glucose transport on 2-FDG-based quantification.
• Introduction of α-methyl-4-deoxy-4-¹⁸F-fluoro-d-glucopyranoside (Me-4FDG) as a potential complementary tracer.

Main Results:

• The lumped constant (LC) is not fixed for a given tissue and can vary significantly, especially in tumors and during disease progression or treatment.
• 2-FDG PET may underestimate or inaccurately represent overall glucose utilization due to its limited interaction with SGLTs.
• Variability in LC can affect the accuracy of prognostic value and treatment monitoring using 2-FDG PET.

Conclusions:

• The assumption of a constant LC for 2-FDG PET may lead to inaccuracies in quantitative glucose metabolism assessment.
• The role of SGLTs in glucose transport necessitates consideration for a more complete understanding of in vivo energetics.
• Combined use of 2-FDG and Me-4FDG may provide a more comprehensive evaluation of glucose utilization through both GLUT and SGLT pathways.