Pre-clinical validation of orthotopically-implanted pulmonary tumor by imaging with 18F-fluorothymidine-positron emission tomography/computed tomography.

The development of positron-emission tomography (PET) and X-ray computed tomography (CT) imaging has improved the detection of tumor burden and, in turn, pre-clinical drug development and clinical treatment. In pre-clinical drug development, clinically-relevant murine cancer models, such as orthotopic models of lung cancer, have provided an accurate representation of tumor burden in humans. However, evidence demonstrating the capability of imaging-guided evaluation of these clinically-relevant models is limited. Here, we combined (18)F-fluorothymidine (FLT)-PET/CT imaging and a murine model of human non-small cell lung cancer (NSCLC) to improve the accuracy of anticancer drug evaluation in pre-clinical studies. We found that FLT-PET/CT imaging enabled the progression of pulmonary tumors to be longitudinally monitored rather than FDG-PET/CT. Furthermore, in an efficacy study of a standard treatment of docetaxel in a murine lung cancer model, FLT-PET imaging detected the anticancer response earlier than volumetric analysis by CT imaging. We, thus, observed a relationship between the alteration of FLT signals and Ki-67 index in the pulmonary tumor during the period of chemotherapy. These results indicate that the combination of FLT-PET/CT imaging and an orthotopic NSCLC model is an effective strategy for evaluating clinical efficacy and potential of an anticancer agent during pre-clinical development.