An exploratory study of volumetric analysis for assessing tumor response with 18 F-FAZA PET/CT in patients with advanced non-small-cell lung cancer (NSCLC)

Background Hypoxia is associated with resistance to chemotherapy and radiotherapy and is randomly distributed within malignancies. Characterization of changes in intratumoral hypoxic regions is possible with specially developed PET tracers such as 18 F-fluoroazomycin arabinoside ( 18 F-FAZA) while tumor metabolism can be measured with 2-deoxy-2-[ 18 F]fluoro- d -glucose ( 18 F-FDG). The purpose of this study was to study the effects of chemotherapy on 18 F-FAZA and 18 F-FDG uptake simultaneously in non-small-cell lung cancer (NSCLC) patients Methods At baseline and after the second chemotherapy cycle, both PET/CT with 18 F-FDG and 18 F-FAZA was performed in seven patients with metastasized NSCLC. 18 F-FAZA and 18 F-FDG scans were aligned with deformable image registration using Mirada DBx. The primary tumors were contoured, and on the 18 F-FDG scan, volumes of interest (VOI) were drawn using a 41 % adaptive threshold technique. Subsequently, the resulting VOI was transferred to the 18 F-FAZA scan. 18 F-FAZA maximum tumor-to-background (T/Bg max ) ratio and the fractional hypoxic volume (FHV) were assessed. Measurements were corrected for partial volume effects. Finally, a voxel-by-voxel analysis of the primary tumor was performed to assess regional uptake differences. Results In the primary tumor of all seven patients, median 18 F-FDG standard uptake value (SUV max ) decreased significantly ( p = 0.03). There was no significant decrease in 18 F-FAZA uptake as measured with T/Bg max ( p = 0.24) or the FHV ( p = 0.35). Additionally, volumetric voxel-by-voxel analysis showed that low hypoxic tumors did not significantly change in hypoxic status between baseline and two cycles of chemotherapy, whereas highly hypoxic tumors did. Individualized volumetric voxel-by-voxel analysis revealed that hypoxia and metabolism were not associated before and after 2 cycles of chemotherapy. Conclusions Tumor hypoxia and metabolism are independent dynamic events as measured by 18 F-FAZA PET and 18 F-FDG PET, both prior to and after treatment with chemotherapy in NSCLC patients.