Abstract
1470
Objectives Accumulating evidence has shown that pretreatment 18F-FDG PET tumor textural features can predict tumor response to chemo/radiotherapy and be associated with patient survival. However, its biologic mechanisms are still largely unknown. The proliferation status of the tumor cells is one of the important factors for tumor responding to chemo/radiotherapy. This study investigated the relationships between the heterogeneity of FDG and FLT uptake. Methods: Twelve patients with newly diagnosed non-small cell lung cancer (NSCLC) underwent pretreatment 18F-FDG and 18F-FLT PET/CT scans within 2~7 days interval. All the tumors have clear boundary on CT images. 18F-FDG and 18F-FLT PET/CT images were carefully co-registered by the corresponding fusion CT images. For textural analysis, regions of interest were drawn manually around the primary tumors on transaxial fusion CT slices. Sixty-four texture parameters describing global (7), local (35), and regional (22) features were measured in addition to four standardized uptake values (SUVs, including maximum, minimum, mean, and peak SUV). Spearman rank correlation (rs) was used to study the relationships between the paired texture features or SUVs for FDG and FLT of the tumor regions on both patient-based and slice-based. RESULTS: The medium tumor volume was 26.9 cm3 (range: 3.6 ~ 121.0 cm3). The medium SUVmax was 8.2 (6.5 ~23.5) for FDG, and 2.8 (1.6 ~ 6.8) for FLT, respectively. On patient-based, no correlation was found between paired SUVs for FDG and FLT. One global, 29 local, and 10 regional texture features in FDG PET were highly positively correlated with those in FLT PET (rs = 0.829~1.0, all P<0.05). On slice-based (126 slices in total), the SUVmin for FDG was weakly correlated with that for FLT per slice (rs = 0.387, P<0.01). Four global, 28 local, and all regional texture features of FDG uptake were positively correlated with those of FLT (rs = 0.301~0.958, all P<0.0001). CONCLUSIONS: Few correlation was found between the SUVs for FDG and FLT in tumor region, but most of texture features describing the spatial and intensity heterogeneity of FDG uptake were positively correlated with those of FLT uptake. This might be one of the biologic mechanisms for the ability of outcome prediction with FDG PET texture analysis.