Diagnostic Value of Diffusion-Weighted MRI for the Detection of Peritoneal and Liver Metastases in High-Risk Pancreatic Ductal Adenocarcinoma: A Prospective Pilot Study.

Abstract

Metastatic presentation is frequent in patients with pancreatic adenocarcinoma and is not always detected on conventional imaging. This study aimed to evaluate the added value of preoperative diffusion-weighted MRI (DWI-MRI) in patients with high-risk pancreatic adenocarcinoma for the detection of peritoneal metastases. This was a prospective single-center pilot study with an aimed sample size of 40 patients. Eligible patients had pancreatic adenocarcinoma, no evidence of distant metastases on preoperative computed tomography (CT) scan, resectable or borderline resectable tumor, and at least one high-risk feature for peritoneal metastases [tumor size ≥ 3 cm and/or carbohydrate antigen 19-9 (CA19-9) ≥ 400 U/mL]. All patients underwent preoperative DWI-MRI. A total of 40 patients were recruited, and 38 patients were included for analysis. Mean tumor size on CT scan was 37.3 mm. Median CA19-9 level was 495 U/mL. DWI-MRI revealed undetected peritoneal metastasis in 5.3% of cases (n = 2), but undetected liver metastases in 34.2% of cases (n = 13). DWI-MRI's sensitivity was 86.7% for liver metastases and 78.9% for overall abdominal metastases. The number needed to treat was 2.9 for the detection of liver metastases, and 2.5 for overall abdominal metastases. Unnecessary surgical exploration was avoided in 39.5% of the cohort. Ultimately, 18 patients were selected for curative-intent surgery, but metastases were found intraoperatively in four additional patients. At 6 months, three additional patients had developed metastatic disease. DWI-MRI revealed few undetected peritoneal metastases, but a significant number of occult liver metastases. Our findings suggest that performing preoperative DWI-MRI in patients with pancreatic adenocarcinoma with high-risk features could be beneficial.