Imaging, Diagnosis, Prognosis Early [F]Fluorodeoxyglucose Positron Emission Tomography at Two Days of Gefitinib Treatment Predicts Clinical Outcome in Patients with Adenocarcinoma of the Lung

Purpose: Positron emission tomography (PET) with [F]fluorodeoxyglucose (FDG) is increasingly used in early assessment of tumor response after chemotherapy. We investigated whether a change in [F]FDG uptake at 2 days of gefitinib treatment predicts outcome in patients with lung adenocarcinoma. Experimental Design: Twenty patients were enrolled. [F]FDG-PET/computed tomographic (CT) scan was carried out before and 2 days after gefitinib treatment. Maximum standardized uptake values (SUV) were measured, and post-gefitinib percentage changes in SUV were calculated. Early metabolic response (SUV decline < 25%) was compared with morphologic response evaluated by CT scan and with progression-free survival (PFS). Results: At 2 days of gefitinib treatment, 10 patients (50%) showedmetabolic response, 8 hadmetabolic stable disease, and 2 had progressivemetabolic disease. Percentage changes of SUV at 2 days were correlated with those of tumor size inCT at 1month (R1⁄40.496;P1⁄4 0.0008).EGFR genewas assessable in 15 patients, and of 12 patients with EGFRmutations, 8 showedmetabolic response at 2 days and 6 showedmorphologic response at 1 month. None of 3 patients with wild-type EGFR showedmetabolic or morphologic response. Metabolic response at 2 days was not statistically associatedwith PFS (P1⁄4 0.095), but when a cutoff value of 20% in SUV decline was used, metabolic responders had longer PFS (P < 0.0001). Conclusion: Early assessment of [F]FDG tumor uptake with PET at 2 days of gefitinib treatment could be useful to predict clinical outcome earlier than conventional CT evaluation in patients with lung adenocarcinoma. Clin Cancer Res; 18(1); 220–8. 2011 AACR.