[18F]-FLT PET to predict early response to neoadjuvant therapy in KRAS wild-type rectal cancer: a pilot study

Object This pilot study evaluated the utility of 3′-deoxy-3′[18F]-fluorothymidine ([ 18 F]-FLT) positron emission tomography (PET) to predict response to neoadjuvant therapy that included cetuximab in patients with wild-type KRAS rectal cancers. Methods Baseline [ 18 F]-FLT PET was collected prior to treatment initiation. Follow-up [ 18 F]-FLT was collected after three weekly infusions of cetuximab, and following a combined regimen of cetuximab, 5-FU, and radiation. Imaging-matched biopsies were collected with each PET study. Results Diminished [ 18 F]-FLT PET was observed in 3/4 of patients following cetuximab treatment alone and in all patients following combination therapy. Reduced [ 18 F]-FLT PET following combination therapy predicted disease-free status at surgery. Overall, [ 18 F]-FLT PET agreed with Ki67 immunoreactivity from biopsy samples and surgically resected tissue, and was predictive of treatment-induced rise in p27 levels. Conclusion These results suggest that [ 18 F]-FLT PET is a promising imaging biomarker to predict response to neoadjuvant therapy that included EGFR blockade with cetuximab in patients with rectal cancer.