Usefulness of 3′-Deoxy-3′-18F-Fluorothymidine PET for Predicting Early Response to Chemoradiotherapy in Head and Neck Cancer

This study compared the utility of 3'-deoxy-3'-(18)F-fluorothymidine PET ((18)F-FLT PET) with that of (18)F-FDG PET for assessment of the early locoregional clinical outcomes of chemoradiotherapy for head and neck squamous cell carcinomas.From May 2006 to September 2010, 28 patients with head and neck squamous cell carcinomas underwent (18)F-FLT and (18)F-FDG PET before radiation therapy (RT), 4 wk after the initiation of RT, and 5 wk after completion of RT. PET images were evaluated qualitatively for regions of focally increased metabolism and were analyzed in relation to residual accumulation and local disease control.During RT, (18)F-FLT uptake decreased more significantly than (18)F-FDG uptake. (18)F-FLT accumulations disappeared in 34 of 54 lesions (63%), and negative predictive value was 97%. (18)F-FDG PET during RT also had a high negative predictive value (100%), but only 9 lesions (16%) showed complete absence of accumulation. The specificity and overall accuracy of (18)F-FLT PET were significantly higher than those of (18)F-FDG PET both during and after RT. In particular, high significance was attributable to the results of the evaluations of primary lesions. There were significant differences in 3-y local control between the residual-accumulation and no-accumulation groups on both posttreatment (18)F-FLT PET (P0.0001) and posttreatment (18)F-FDG PET (P = 0.0081).(18)F-FLT PET during RT and early follow-up facilitates the selection of optimal further therapy and the prediction of outcomes.