PET imaging with [18F]3′-deoxy-3′-fluorothymidine for prediction of response to neoadjuvant treatment in patients with rectal cancer
Positron emission tomography (PET) using 18F-labelled 3′-deoxy-3′-fluorothymidine (FLT) was assessed for therapy monitoring in patients with rectal cancer undergoing neoadjuvant chemoradiotherapy.
Ten patients with locally advanced rectal cancer were included and underwent long-course preoperative chemoradiotherapy (total dose 45 Gy, 1.8 Gy/day, concomitant 250 mg/m2 5-fluorouracil) followed by surgery. FLT-PET was performed prior to chemoradiotherapy, 2 weeks after initiation of chemoradiotherapy and preoperatively (3–4 weeks post chemoradiotherapy). FLT uptake was correlated with histopathological tumour regression and changes in T stage.
Mean tumour FLT uptake was 4.2±1.0 SUV before therapy and decreased significantly to 2.9 ± 0.6 SUV 14 days after initiation of chemoradiotherapy (−28.6% ± 10.7%, p = 0.005). The preoperative scan showed a further decrease to 1.9 ± 0.4 SUV (−54.7% ± 7.6%, p = 0.005). However, the degree of change in FLT uptake 2 weeks after initiation and after completion of neoadjuvant therapy did not correlate with histopathological tumour regression.
FLT-PET did not seem to be a promising method for assessment of tumour response in the studied chemoradiotherapy regimen in patients with rectal cancer.
KeywordsRectal cancer Therapy monitoring FLT-PET Proliferation
We acknowledge the efforts of the cyclotron and radiochemistry staff. We appreciate the excellent technical support offered by the technologists at our institution. We thank Jeffrey Fessler, PhD, University of Michigan, for generously providing the software for the iterative reconstruction of the PET studies.
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