Localized FDG loss in lung cancer lesions

Area of Science:

• Nuclear Medicine
• Oncology
• Radiochemistry

Background:

• Standard [18F]-Fluorodeoxyglucose (FDG) kinetic analysis in cancer is limited to average uptake.
• Tumor lesions contain inflammatory cells that exhibit FDG washout due to FDG-6P hydrolysis.
• Glucose-6P phosphatase activity contributes to tracer washout in specific tumor regions.

Purpose of the Study:

• To determine if voxel-wise compartmental analysis of dynamic PET imaging can identify tumor regions with tracer washout.
• To investigate the prevalence and location of tracer washout patterns within lung cancer lesions.
• To assess the potential of this method for monitoring cancer treatment efficacy.

Main Methods:

• 11 lung cancer patients underwent dynamic PET/CT imaging.
• Tumor volumes of interest were defined based on standardized uptake value (SUV) thresholds.
• Voxel-wise compartmental analysis using Patlak regression was performed on parametric maps generated from dynamic imaging data.
• Analysis involved progressively delaying the starting frame to identify washout patterns.

Main Results:

• Delaying the analysis start point increased the prevalence of voxels showing negative slope (tracer washout).
• In the most delayed analysis, washout voxels constituted a median of 2% of tumor volume (0.5-4.5%).
• This washout pattern was observed at lesion borders and was independent of tumor size.

Conclusions:

• Voxel-wise parametric maps can identify measurable volumes with radioactivity washout within tumors.
• The spatial distribution of washout is consistent with inflammatory infiltrates in the tumor stroma.
• This technique may improve the monitoring of immunotherapies aimed at enhancing the host immune response against cancer.