Combined uptake of [18F]FDG and [18F]FMISO correlates with radiation therapy outcome in head-and-neck cancer patients

PurposeFDG PET is frequently used for radiotherapy (RT) planning to determine the tumour extent. Similarly, FMISO is used to assess the hypoxic sub-volume. The relationship between the volumes determined on the basis of FDG and FMISO was investigated. Additionally, the quantitative correlation of the tracers on a voxel basis was studied.MethodsTwelve head-and-neck cancer (HNC) patients underwent FDG and FMISO PET examinations prior to RT treatment. The tumour volumes assessed by the two tracers and also the voxel-based joint uptake values were investigated. The characteristic shapes and patterns of the determined scatter plots were analyzed.A number of different variables such as the maximum uptake values of FDG and FMISO, the FDG and FMISO positive volumes, the slope m of the regression line and the scatter width σ of the scatter plots were tested for their ability to stratify the patient group with respect to treatment outcome.ResultsA diversity of characteristic FDG-FMISO distributions was observed in the patient group. However, no general correlation of enhanced glucose metabolism and FMISO uptake was observed.The maximum uptake of FMISO (p = 0.045) showed borderline significance for stratifying the patient group. FDG positive tumour volume, hypoxic fraction, maximum FDG uptake and m were not significant. σ turned out to be the most significant variable (p = 0.008) to predict treatment success probabilities.ConclusionFMISO and FDG PET data provide independent information about the examined tumour. A quantification of the correlated tracer uptake seems to be meaningful.