Simultaneous positron emission tomography (PET) assessment of metabolism with 18F-fluoro-2-deoxy-D-glucose (FDG), proliferation with 18F-fluoro-thymidine (FLT), and hypoxia with 18fluoro-misonidazole (F-miso) before and during radiotherapy in patients with non-small-cell lung cancer (NSCLC): A pilot study

Objectives: To investigate the changes in tumour proliferation (using FLT), metabolism (using FDG), and hypoxia (using F-miso) during curative (chemo-) radiotherapy (RT) in patients with non-small-cell lung cancer (NSCLC). Patients and methods: Thirty PET scans were performed in five patients (4 males, 1 female) that had histological proof of NSCLC and were candidates for curative-intent RT. Three PET-CT (Biograph S16, Siemens) scans were performed before (t(0)) and during (around dose 46 Gy, t(46)) RT with minimal intervals of 48 h between each PET-CT scan. The tracers used were (18)fluoro-2deoxyglucose (FDG) for metabolism, (18)fluorothymidine (FLT) for proliferation, and F-18-misonidasole (F-miso) for hypoxia. The 3 image sets obtained at each time point were co-registered (rigid: n = 9, elastic: n = 1, Leonardo, TrueD, Siemens) using FDG PET-CT as reference. VOIs were delineated (40% SUVmax values were used as a threshold) for tumours and lymph nodes on FDG PET-CT, and they were automatically pasted on FLT and F-miso PET-CT images. ANOVA and correlation analyses were used for comparison of SUVmax values. Results: Four tumours and twelve nodes were identified on initial FDG PET-CT images. FLT SUVmax values were significantly lower (p < 0.0006) at t(46) in both tumours and nodes. The decrease in FDG SUVmax values had a trend towards significance (p = 0.048). F-Miso SUVmax values were significantly higher in tumours than in nodes (p = 0.02) and did not change during radiotherapy (p = 0.39). A significant correlation was observed between FLT and FDG uptake (r = 0.56, p < 10(-4)) when all data were pooled together, and they remained similar when the before and during RT data were analysed separately. FDG and F-miso uptakes were significantly correlated (r = 0.59, p = 0.0004) when all data were analysed together. The best fit was obtained after adjusting for lesion type (tumour vs. node). This correlation was observed for the SUVmax measured during RT (r = 0.70, p = 0.008) but not for the pre-RT data (r = 0.19, p = 0.35). The weak correlation between FLT and F-miso uptakes only became significant (r = 0.66, p = 0.002) when the analysis was restricted to the data acquired during RT. Conclusion: Three different PET acquisitions can be performed quasi-simultaneously (4-7 days) before and during radiotherapy in patients with NSCLC. Our results at 46 Gy suggest that a fast decrease in the proliferation of both tumours and nodes exists during radiotherapy with differences in metabolism (borderline significant decrease) and hypoxia (stable). (C) 2010 Elsevier Ireland Ltd. All rights reserved. Radiotherapy and Oncology 98 (2011) 109-116