Objective: The aim of this study was to investigate the feasibility of F-fluoroazomycinarabinofuranoside (F-FAZA) positron emission tomography (PET)/computed tomography (CT) in patients with locally advanced rectal cancer.
Materials and methods: The study included 14 patients with locally advanced rectal cancer. Before chemoradiotherapy, PET/CT with F-FAZA was performed with static 15 min images 2 h after injection of F-FAZA. Attenuation correction was obtained with a low-dose CT, and a contrast-enhanced CT was performed immediately after the PET scan.
Results: F-FAZA uptake [mean and maximum standardized uptake value (SUVmean) and (SUVmax)] was significantly higher in rectal tumours than in both muscles (P<0.003) and normal intestinal walls (P<5×10). The tumour to muscle (T/M) ratios ranged from 1.19 to 3.05 with a mean of 1.97, whereas the tumour to intestinal wall (T/I) ratios had values of 1.73-5.81 with a mean of 2.83. Intense activity accumulating in the bladder produced obvious scattered activity, which spread into the surrounding tissue. Tumour volumes excluding scatter were therefore determined, in which the SUVmax and SUVmean were also significantly higher than in both muscles (P<0.004) and normal intestinal walls (P<2×10) and had T/M ratios of 1.19-2.72 with a mean of 1.85 and T/I ratios of 1.71-5.40 with a mean of 2.67. The individual SUVmax, SUVmean, T/M and T/I values were significantly higher in the entire tumour volume compared with the tumour volume adjusted for scatter from the urinary bladder (P<0.005), although the absolute differences were small.
Conclusion: F-FAZA PET/CT is feasible for visualization of hypoxia in patients with rectal cancer, but scattered activity from the urinary bladder should be taken into consideration.