The goal of this study was to evaluate the effectiveness of dynamic PET imaging on the assessment of early therapeutic response in patients with oral cavity squamous carcinoma. The kinetic parameters derived from pre- and post-treatment dynamic scans were used to predict clinical outcome and compared with SUV using survival as gold standard.
Twenty-five patients underwent dynamic 18F-FDG PET/CT scans before the onset of concurrent chemo-radiotherapy (CCRT) and after the completion of first cycle (7 days gap). The changes in Patlak-derived FDG influx rates (Ki) were retrieved and compared with the changes of standardized uptake values (SUVs) which were measured on the last frame of each dynamic image series. Receiver operating characteristic curve (ROC) was then used to characterize the prognosis accuracy of percentage change of Ki/SUVs.
We used 5-year survival to categorize the patients into 2 groups: response (n=16) and nonresponse (n=9). The influx rate Ki derived from dynamic 18F-FDG PET significantly decreased one week after initiation of treatment in responders ( 0.12 ± 0.05 for pre-treatment, 0.05 ± 0.02 for post-treatment; P = 0.005). 18F-FDG SUV values did not demonstrate similar capability in responders (pre 9.57 ± 4.56, post 6.18 ± 2.64; P = 0.1). Neither Ki nor SUV showed significant decrease after early treatment in non-responders. With regard to the individual changes (%), Ki could differentiate the responders from non-responders (p=0.009), while SUV couldn’t (p=0.6). ROC analysis confirms that Ki yielded identification of responsive vs nonresponsive subjects with an area under curve (AUC) of 0.89 (95% confidence interval) which is significantly superior to FDG SUV (AUC = 0.63).
Quantitative parameter Ki derived from 18F-FDG dynamic PET/CT has great potential on the early assessment of therapeutic response in oncological patients.