Oral contrast material [Diatrizoate sodium meglumine (Gastrografin; Bayer Hispania, SL, Saipan)] was administered before the study to achieve an adequate colonic opacification and distention. Intravenous non-ionic contrast agent (Omnipaque® 300 mg iodine/mL; Nycomed, Hispania, SL, Saipan) was also administered. The standard CT acquisition protocol was performed in the venous phase—start delay of 70 seconds—to maximize the detection

of eventual hepatic metastases. A section of 5 mm width was performed. An intraluminal lesion with wall thickening but without surrounding Inhibitors,research,lifescience,medical tissue infiltration was defined as a T2 classification. Spiculated tissue extending from the colonic wall into the Inhibitors,research,lifescience,medical pericolic fat was characterized as a T3 classification. Colonic wall masses with infiltration

of other surrounding organs were considered as T4 classification. Regional lymph node >0.8 cm in short axis diameter were considered pathologic. The tumor volume was measured using semiautomatic segmentation dedicated software (Volume Wizard®, Siemens Inhibitors,research,lifescience,medical Medical Solutions, Erlangen, Germany). In CT, absolute Hounsfield units (HU) correspond directly to the tissue property. Thus, a predefined soft tissue window display setting (300 to 45 HU) was applied to determine the tumor volume. The tumor was manually defined and segmentation of the entire scanning volume was performed automatically, with manual adjustments when necessary. The tumor was measured across the total imaging volume and calculated in cubic centimeters (cc). Figure 1 shows the tumor volume estimation. Inhibitors,research,lifescience,medical Figure 1 Tumor volume estimation by CT scan. CT, computed tomography.

PET-CT scan protocol Patients were required to fast for 6 h. A blood glucose analysis was performed to ensure that levels were under 120 mg/dL. All patients received an intravenous injection of 6.29 MBq/kg of (18F)-FDG. One hour after the injection, (18F)-FDG-PET/CT studies were performed using a Biograph DUO scanner (Siemens, Knoxville, TN, USA). PET emission images were Inhibitors,research,lifescience,medical acquired with patients in a supine position using the 3-D mode (field of view 50 cm in the transaxial plane and 15.5 cm in the axial plane), at three min per bed position. CT data were used for attenuation correction and anatomical already location of PET emission data. Quantitative measurement was normalized for the dose administered and the weight of the patients [standardized uptake value (SUV)]. Response evaluation A CT (or PET-CT) scan was repeated 3-4 weeks after the end of neoadjuvant chemotherapy in order to assess tumour response and to confirm the resectability. Radiologic response The percentual tumor volume differences were calculated by CT. Three response categories were established: minor (volume reduction <33%), medium (33-66%) and major (>66%). Changes in T and N classification were also find more recorded.