IMAGING CELLULAR PROLIFERATION DURING CHEMO-RADIOTHERAPY: A PILOT STUDY OF SERIAL 18F-FLT POSITRON EMISSION TOMOGRAPHY/COMPUTED TOMOGRAPHY IMAGING FOR NON-SMALL-CELL LUNG CANCER

Purpose: To establish whether F-18-3'-deoxy-3'-fluoro-L-thymidine (F-18-FLT) can monitor changes in cellular proliferation of non-small-cell lung cancer (NSCLC) during radical chemo-radiotherapy (chemo-RT). Methods and Materials: As part of a prospective pilot study, 5 patients with locally advanced NSCLC underwent serial F-18-FLT positron emission tomography (PET)/computed tomography (CT) scans during treatment. Baseline F-18-FLT PET/CT scans were compared with routine staging F-18-FDG PET/CT scans. Two on-treatment F-18-FLT scans were performed for each patient on Days 2,8,15 or 29, providing a range of time points for response assessment. Results: In all 5 patients, baseline lesional uptake of F-18-FLT on PET/CT corresponded to staging F-18-FDG PET/CT abnormalities. F-18-FLT uptake in tumor was observed on five of nine (55%) on-treatment scans, on Days 2, 8 and 29, but not Day 15. A "flare" of F-18-FLT uptake in the primary tumor of one case was observed after 2 Gy of radiation (1.22 x baseline). The remaining eight on-treatment scans demonstrated a mean reduction in F-18-FLT tumor uptake of 0.58 x baseline. A marked reduction of F-18-FLT uptake in irradiated bone marrow was observed for all cases. This reduction was observed even after only 2 Gy, and all patients demonstrated a complete absence of proliferating marrow after 10 Gy. Conclusions: This proof of concept study indicates that F-18-FLT uptake can monitor the distinctive biologic responses of epithelial cancers and highly radiosensitive normal tissue changes during radical chemo-RT. Further studies of F-18-FLT PET/CT imaging during therapy may suggest that this tracer is useful in developing response-adapted RT for NSCLC. Crown Copyright (C) 2009 Published by Elsevier Inc.