Correlation of Iodine Quantification and FDG Uptake in Early Therapy Response Assessment of Non-small Cell Lung Cancer: Possible Benefit of Dual-energy CT Scan as an Integral Part of PET/CT Examination.

Aim: To compare iodine-related and fluorine-18 fluorodeoxyglucose (F-FDG) parameters during staging of lung cancer as well as during early follow-up, while investigating potential use and possible substitutability in the assessment of therapeutic response or prediction.

Patients And Methods: Patients (n=45) with confirmed lung cancer underwent F-FDG positron-emission tomography (PET) using single-source dual-energy computed tomography was performed for staging and early follow-up. Correlation of FDG uptake and iodine-related parameters was assessed and comparison with therapy response was performed.

Results: A strong correlation was found between the volumetric FDG parameters metabolic tumour volume (MTV) and total lesion glycolysis (TLG) and iodine uptake (IU) in staging (IU vs. MTV: r=0.894; p<0.001 and IU vs. TLG: r=0.874; p<0.001) and follow-up (IU vs. MTV: r=0.934, p<0.001 and IU vs. TLG: r=0.935, p<0.001). We also found significant correlation of change in these values between timepoints. We observed a significant correlation of IU, MTV and TLG with early therapy response and IU was found as a possible strong predictor.

Conclusion: Strong correlation of IU and volume-based FDG parameters was proved in staging, follow-up and change during therapy. Potential role of IU in prediction of early therapy-response was identified. Our study suggests a significant benefit of using the dual-energy computed tomography as a part of F-FDG PET/CT in patients with lung cancer.