¹⁸F-FDG PET/CT for monitoring treatment responses to the epidermal growth factor receptor inhibitor erlotinib

Response rates of unselected non-small cell lung cancer (NSCLC) patients to the epidermal growth factor receptor inhibitor erlotinib are low and range from 10%to 20%. Early response assessments are needed to avoid costs and side effects of inefficient treatments. Here we determined whether early changes in tumor uptake of ¹⁸F-FDG can predict progression-free and overall survival in NSCLC patients who are treated with erlotinib. Methods: Twenty-two patients (6 men, 16 women; mean age ± SD, 64 ± 13 y) with stage III or stage IV NSCLC who received erlotinib treatment were enrolled prospectively. ¹⁸F-FDG PET/CT was performed before the initiation of treatment (n = 22), after 2 wk (n = 22), and after 78 ± 21 d (n = 11). Tumor maximum standardized uptake values were measured for a maximum of 5 lesions for each patient. Tumor responses were classified using modified PET Response Criteria in Solid Tumors (use of maximum standardized uptake values). Median overall survival by Kaplan-Meier analysis was compared between groups using a log-rank test. Results: The overall median time to progression was 52 d (95% confidence interval, 47-57 d). The overall median survival time was 131 d (95% confidence interval, 0-351 d). Patients with progressive metabolic disease on early follow-up PET showed a significantly shorter time to progression (47 vs. 119 d; P < 0.001) and overall survival (87 vs. 828 d; P = 0.01) than patients classified as having stable metabolic disease or partial or complete metabolic response. Conclusion: These data suggest that ¹⁸F-FDG PET/CT performed early after the start of erlotinib treatment can help to identify patients who benefit from this targeted therapy.