Radiolabelled leukocytes are useful for the imaging of inflammation and infection, and 18F-fluorodeoxyglucose (18F-FDG) is known to concentrate in metabolically active cells. We evaluated the feasibility of leukocyte labelling with 18F-FDG using ACD and heparin anticoagulants at 20 degrees C and 37 degrees C, with and without gentle mixing during incubation. With leukocytes (WBC) harvested from 20 ml blood, studies were performed using 18F-FDG in concentrations of 3.7-74 MBq (0.1-2.0 mCi). 18F-FDG WBC stability in platelet-poor plasma was assessed at 1-4 h. Satisfactory labelling efficiency was achieved with incubation in heparin-saline at 37 degrees C for 30 min (62.7+/-1.6%), and was further enhanced by mixing during incubation (78.1+/-3.9%). Cell labelling was predominantly of granulocytes (78.5+/-1.4%). 18F-FDG WBC was relatively stable in platelet-poor plasma for up to 4 h, and no cell staining was observed in viability studies using trypan blue. These results indicate the feasibility of leukocyte labelling with 18F-FDG, providing an approach that may be useful in PET imaging of inflammation and infection.

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Objective: We prospectively compared FDG-PET and FLT-PET in assessing patient responses to induction cetuximab and/or chemoradiotherapy (CRT) for advanced head and neck squamous cell carcinoma (HNSCC) and esophageal cancer (EC). Methods:Sixteen patients were enrolled, 9 with HNSCC and 7 with EC. FDG-PET and FLT-PET scans were performed at baseline and two weeks into chemoradiotherapy (CRT) for patients with EC. Patients with HNSCC received two weeks of induction chemotherapy along with post-induction PET scans prior to starting CRT in addition to the baseline and intra-chemoradiotherapy PET scans. Changes in SUVmax and total lesion glycolysis/ proliferation (TLG/TLP) were compared with baseline.Results: Median follow-up for living patients was 6.0 years. Median overall survival (OS) was 3.3 years and progression-free survival (PFS) was 2.5 years. Patients with HNSCC had higher baseline SUVmax, TLG and TLP than those with EC. Changes in SUVmax, TLG and TLP after induction chemotherapy or during CRT did not correlate with PFS or OS. Those with >40% decline in SUVmax on FDG-PET six weeks after completing CRT had better PFS (p<0.0001) and OS (p=0.0003) than those with less of a response. In addition, >70% decrease in posttreatment TLG correlated with better PFS (p=0.03) and OS (p=0.04). Conclusions:Functional imaging performed early during chemoradiotherapy for advanced HNSCC and EC is feasible. Changes on post-induction and intra-CRT FLT and FDG PET did not correlate with PFS or OS. However, better PFS and OS were seen in patients with >40% decline in SUVmax and >70% decrease in TLG on FDG-PET performed six weeks after completing CRT. Further research is needed to determine the prognostic impact of PET performed during chemotherapy and radiotherapy.