Is F-18-FDG PET/CT Useful for the Early Prediction of Histopathologic Response to Neoadjuvant Erlotinib in Patients with Non-Small Cell Lung Cancer?

Early prediction of treatment response is of value in avoiding the unnecessary toxicity of ineffective treatment. The objective of this study was to prospectively evaluate the role of integrated F-18-FDG PET/CT for the early identification of response to neo-adjuvant erlotinib, an epidermal growth factor receptor tyrosine kinase inhibitor. Methods: From October 2006 to March 2009, 23 patients with non-small cell lung cancer eligible for surgical resection were evaluated for this study. Patients received preoperative erlotinib (150 mg) once daily for 3 wk. 18F-FDG PET/CT was performed before and at 1 wk after the administration of erlotinib. Changes in tumor F-18-FDG uptake during treatment were measured by standardized uptake values and assessed prospectively according to the criteria of the European Organization for Research and Treatment of Cancer. Patients with a decrease in standardized uptake values of 25% or more after 1 wk were classified as metabolic responders. The metabolic response was compared with the pathologic response, obtained by histopathologic examination of the resected specimen. Results: Following the F-18-FDG PET/CT criteria of the European Organization for Research and Treatment of Cancer, 6 patients (26%) had a partial response within 1 wk, 16 patients (70%) had stable disease, and 1 patient (4%) had progressive disease. The median percentage of necrosis in the early metabolic responder group was 70% (interquartile range, 30%-91%), and the median percentage of necrosis in the nonresponder group was 40% (interquartile range, 20%-50%; P = 0.09). The kappa-agreement between the metabolic and pathologic responders was 0.55 (P = 0.008). Conclusion: The results of this study suggest that early during the course of epidermal growth factor receptor tyrosine kinase inhibitor therapy, F-18-FDG PET/CT can predict response to erlotinib treatment in patients with non-small cell lung cancer.