Whole‐body MRI with diffusion‐weighted imaging as an adjunct to18F‐fluorodeoxyglucose positron emission tomography and CT in patients with suspected recurrent colorectal cancer.

Aim: The aim was to explore how findings of whole‐body MRI including diffusion‐weighted imaging (DW‐MRI) compared to the routine diagnostic workup with CT and/or 18F‐fluorodeoxyglucose (FDG) positron emission tomography (PET)/CT in patients with suspected recurrent colorectal cancer (CRC). Method: This was an exploratory retrospective analysis of 55 patients with a clinical suspicion of recurrent CRC who underwent DW‐MRI following CT and/or FDG‐PET/CT. Two readers in consensus interpreted all clinical imaging reports and converted each described lesion into a confidence score (1 = definitely benign to 5 = definitely malignant). DW‐MRI findings were compared to the most recent previous CT or PET/CT. Any discrepant or additional DW‐MRI findings were documented and compared with histology and/or clinical follow‐up (if available). Results: Whole‐body MRI including diffusion‐weighted imaging (DW‐MRI) resulted in discrepant/additional findings in 26/55 (47%) cases; 23/37 (62%) compared to previous CT and 3/18 (17%) compared to previous PET/CT. These included 10 cases where DW‐MRI converted previously inconclusive CT (n = 8) or PET/CT (n = 2) findings into a conclusive diagnosis, one where it contradicted a previous CT diagnosis of recurrence, five where DW‐MRI diagnosed recurrent disease not previously reported on CT and 10 cases where DW‐MRI detected additional lesions compared to CT (n = 9) or PET/CT (n = 1). Eighty‐eight per cent of cases with discrepant/additional findings concerned patients with recurrent/metachronous peritoneal metastases. In total, DW‐MRI resulted in 42 discrepant/additional lesions; the DW‐MRI diagnosis was correct in 76% of these lesions and incorrect (false positive) in 7%. In the remaining 17%, no standard of reference was available. Conclusions: This explorative study suggests that DW‐MRI may be of added value to patients with a clinical suspicion for recurrent CRC, in particular to identify patients with peritoneal metastases. DW‐MRI mainly has potential as a 'problem‐solver' in patients with inconclusive or negative findings on previous imaging (in particular CT) and to detect additional disease sites in patients already diagnosed with recurrent disease. [ABSTRACT FROM AUTHOR]