3'-deoxy-3'-(18)F-fluorothymidine (FLT) positron emission tomography for early prediction of response to chemoradiotherapy--a clinical application model of esophageal cancer.

Early detection of response to neoadjuvant chemoradiation in esophageal cancer may allow individualization of treatment strategies and avoidance of unnecessary treatment. Although positron emission tomography (PET) with [(18)F]fluorodeoxyglucose (FDG) permits detection of changes in tumor proliferation before any change in tumor size is evident, FDG-PET may fail to distinguish between residual tumor and inflammation and between complete response and partial response with substantial residual tumor burden. PET with the nucleoside analogue 3'-deoxy-3'-(18)F-fluorothymidine (FLT) is more accurate than FDG-PET in visualizing early changes in tumor proliferation. In a recent study in experimental models of esophageal cancer, FLT-PET was more accurate than FDG-PET in detecting early changes in proliferation following docetaxel and radiation therapy in human SEG-1 cells and mouse SEG-1 xenografts, including having a much stronger correlation with histologic findings. Clinical studies are needed to determine if FLT-PET can distinguish among degrees of response to neoadjuvant chemoradiation in patients with esophageal cancer. The ability to visualize tumor cell proliferation may also contribute to the ability to improve precision delivery of radiation therapy.