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

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.FDG uptake is increased in the colon of DTC patients treated by sorafenib.Sorafenib is a new targeted therapy with an angiogenesis inhibiting activity, belonging to the tyrosine kinase inhibitors (TKI) family [1]. This multikinase inhibitor has been evaluated in various cancers with promising results [2-4], including in medullary [5] and in differentiated thyroid cancer (DTC) [6,7]. In the first patients with DTC treated by sorafenib in our unit, we often noticed an intense and diffuse 18-Fluorodeoxyglucose (FDG) uptake in the abdomen. The aim of the present retrospective work was to assess the proportion of patients with such an uptake, to determine the uptake pattern in the small intestine and in the colon, to evaluate the scintigraphic outcome pattern after sorafenib withdrawal when possible and to compare this uptake with that of patients treated by other TKI such as sunitinib and vandetanib.Between June 2008 and July 2011, 169 FDG PET/CT studies were performed in 85 patients with DTC. Among these, 61 PET/CT studies were selected for analysis and pooled in the three following groups. Group 1 included 20 PET/CT studies performed in six patients with radioiodine negative progressive metastatic disease treated by sorafenib. The control group (group 2) included 26 PET/