Sorafenib increases 18-FDG colic uptake: demonstration in patients with differentiated thyroid cancer

BACKGROUND: To assess 18-fluorodeoxyglucose (FDG) bowel uptake in patients with differentiated thyroid cancer (DTC) treated with sorafenib. FINDINGS: Visual (5-point scale) and high maximum standard uptake value (SUVmax) semi-quantitative analyses were conducted in 63 positron emission tomography (PET) studies performed in patients on sorafenib (group 1, n = 20), in a control group (group 2, n = 28) and in patients on sunitinib or vandetanib (group 3, n = 15). Moderate or high and diffuse bowel uptake (grade 4 or 5) was observed in 90% of the PET scans of group 1 versus none in group 2. Only 20% of PET scans in group 3 were scored grade 4. SUVmax values were significantly higher for all colic segments in group 1 than in group 2 (P < 0.0001) or 3 (P < 0.0004). This uptake pattern appeared rapidly (one month) and disappeared after sorafenib withdrawal. CONCLUSIONS: FDG uptake is increased in the colon of DTC patients treated by sorafenib.