Early assessment of radiation response using a novel functional imaging modality -- [18F]fluorocholine PET (FCH-PET): a pilot study.

[¹⁸F]Fluorodeoxyglucose-positron emission tomography/computerized tomography (FDG-PET) is commonly used to assess response to patients treated with radiation (RT) or combination of chemotherapy and RT (CRT). The intent of this pilot study is to explore whether [¹⁸F]fluorocholine PET (FCH-PET) can serve as an early predictive biomarker for early detection of RT/CRT response. Fourteen patients have been accrued and analyzed. The lesions were base of tongue, tonsil, nodes, hypopharynx, maxilla, palate, lung, pancreas, brain, uterine, and rectal. There were 16 lesions that were considered target lesion and were followed for correlation between change in FCH-PET SUVmax readings and clinical outcome. Median tumor size was 4.4 cm. Median RT dose was 66 Gy. The change in SUVmax (Δ SUVmax) of FCH-PET scans performed before and during RT was correlated with clinical outcome at the last follow-up. The median FCH-PET SUVmax for the 1st and 2nd scans was 6.15 and 4.65, respectively. Fourteen (87.5%) lesions showed a reduction in SUVmax in either a complete response (CR) or a partial response (PR), and 2 lesions showed an increase in SUVmax both of which were determined to be non-response (NR). The median percentage change between the 1st and 2nd scan was -19.5%. Forty-four percent of lesions (7/16) had CR, 44% (7/16) had PR, and 12% (2/16) had NR (no response). Median follow-up was 12 months. The results showed a difference between NR and PR, between NR and CR, and a trend towards significance (p=0.06). FCH-PET scan demonstrated changes in SUVmax during RT that were predictive of final outcome.