Timing of metabolic response monitoring during erlotinib treatment in non-small cell lung cancer

The purpose of this study was to prospectively evaluate the timing of metabolic response monitoring with ¹⁸F-FDG PET of (neoadjuvant) erlotinib treatment in patients with early-stage non-small cell lung cancer. Methods: This study was designed as an open-label phase II trial performed in 4 hospitals in The Netherlands. Patients received preoperative erlotinib (150 mg) once daily for 3 wk. Response evaluation was performed after 4-7 d and at 3 wk with ¹⁸F-FDG PET/CT scans. Tumor ¹⁸F-FDG uptake and changes were measured as standardized uptake values (SUVs). The metabolic response was classified on the basis of European Organization for Research and Treatment of Cancer criteria (>25% decrease in the maximum SUV) and was compared with histopathologic regression as observed in the resection specimen. Results: From December 2006 to November 2010, 60 patients with non-small cell lung cancer eligible for surgical resection were enrolled in this study. For 43 patients (18 men and 25 women), baseline ¹⁸F-FDG PET/CT scans as well as both monitoring scans and histopathologic response monitoring were available. A partial metabolic response on ¹⁸F-FDG PET/CT scans was observed for 10 patients (23%) after 1 wk and for 14 patients (33%) after 3 wk. Histopathologic examination revealed regression (necrosis of >50%) in 11 patients (26%). In these patients, the maximum SUV decreased by a mean of 17% within 1 wk and a mean of 31% at 3 wk. Seven patients were identified as responders within 1 wk. Conclusion: Response monitoring with ¹⁸F-FDG PET/CT within 1 wk after the start of erlotinib treatment identified approximately 64% of histopathologic responders on the basis of European Organization for Research and Treatment of Cancer criteria.