Combined use of 18F-FDG PET/CT, DW-MRI, and DCE-MRI in treatment response for preoperative chemoradiation therapy in locally invasive rectal cancers.

We investigated if 18F-FDG PET/CT, DW-MRI, and DCE-MRI are able to predict preoperative chemoradiation therapy (CRT) response in patients with T3-4 rectal adenocarcinomas. MRI and PET/CT scans were performed within 1 week, at baseline, early midtreatment (2 weeks of CRT), and posttreatment (6 weeks after completing CRT). Responders (n = 4) and nonresponders (n = 4) were defined according to tumor regression grade by histology. Only SUVmax (P = 0.030) at early midtreatment could significantly differentiate between responders and nonresponders, suggesting that 18F-FDG PET/CT may be effective to predict early treatment response compared with DW-MRI and DCE-MRI in T3-4 rectal cancer.