Predictive value of early and late residual 18F-fluorodeoxyglucose and 18F-fluorothymidine uptake using different SUV measurements in patients with non-small-cell lung cancer treated with erlotinib.

PURPOSE: To evaluate the predictive value of early and late residual (18)F-fluorodeoxyglucose (FDG) and (18)F-fluorothymidine (FLT) uptake using different SUV measurements in PET in patients with advanced non-small-cell lung cancer (NSCLC) treated with erlotinib.

METHODS: We retrospectively reviewed data from 30 patients with untreated stage IV NSCLC who had undergone a combined FDG PET and FLT PET scan at 1 week (early) and 6 weeks (late) after the start of erlotinib treatment. Early and late residual FDG and FLT uptake were measured in up to five lesions per scan with different quantitative standardized uptake values (SUV(max), SUV(2Dpeak), SUV(3Dpeak), SUV(50), SUV(A50), SUV(A41)) and compared with short-term outcome (progression vs. nonprogression after 6 weeks of erlotinib treatment). Receiver-operating characteristics (ROC) curve analysis was used to determine the optimal cut-off value for detecting nonprogression after 6 weeks. Kaplan-Meier analysis and the log-rank test were used to evaluate the association between residual uptake and progression-free survival (PFS).

RESULTS: Nonprogression after 6 weeks was associated with a significantly lower early and late residual FDG uptake, measured with different quantitative parameters. In contrast, nonprogression after 6 weeks was not associated with early and late residual FLT uptake. Furthermore, patients with a lower early residual FDG uptake measured in terms of SUV(max) and SUV(2Dpeak) had a significantly prolonged PFS (282 days vs. 118 days; p = 0.022) than patients with higher values. Similarly, lower late residual FDG uptake and early residual FLT uptake measured in terms of SUV(3Dpeak), SUV(A50) and SUV(A41), and late FLT uptake measured in terms of SUV(3Dpeak) and SUV(A50) was associated with an improved PFS.

CONCLUSION: Early and late residual FDG uptake, measured using different quantitative SUV parameters, are predictive factors for short-term outcome in patients with advanced NSCLC treated with erlotinib. Additionally, low residual FDG and FLT uptake early and late in the course of erlotinib treatment is associated with improved PFS.