Accuracy of Whole-Body Diffusion-Weighted MRI (WB-DWI/MRI) in Diagnosis, Staging and Follow-Up of Gastric Cancer, in Comparison to CT: A Pilot Study. 

Abstract Background: Accurate staging of patients with gastric cancer is necessary for selection of the most appropriate and personalized therapy. Computed Tomography (CT) is currently used as primary staging tool, being widely available with a relatively high accuracy for the detection of parenchymal metastases, but with low sensitivity for the detection of peritoneal metastases. Magnetic resonance imaging (MRI) with diffusion-weighted imaging (DWI) has a very high spatial and contrast resolution, suggesting a higher diagnostic performance in the detection of small peritoneal lesions. The aim of this study was to retrospectively evaluate the added value of whole-body diffusion-weighted MRI (WB-DWI/MRI) to CT for detection of peritoneal carcinomatosis (PC) and distant metastases in the preoperative staging of gastric cancer.Methods: This retrospective study included thirty-two patients with a suspicion of gastric cancer/recurrence, who underwent WB-DWI/MRI at 1.5 Tesla, in addition to CT of thorax and abdomen. Images were evaluated by two experienced abdominal radiologists in consensus. Histopathology, laparoscopy and/or 1-year follow-up were used as reference standard.Results: For overall tumor detection (n=32), CT sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) was 83.3%, 100%, 100% and 82.4% respectively. For WB-DWI/MRI these values were 100%, 92.9%, 94.7% and 100%, respectively. For staging (n=18) malignant lymph nodes and metastases, CT had a sensitivity, specificity/ PPV/ NPV of 50%/ 100%/ 100%/ 71.4%, and 15.4%/ 100%/ 100%/ 31.3% respectively. For WB-DWI/MRI, all values were 100%, for both malignant lymph nodes and metastases. WB-DWI/MRI was significantly better than CT in detecting tumor infiltration of the mesenteric root, serosal involvement of the small bowel and peritoneal metastases for which WB-DWI/MRI was correct in 100% of these cases, CT 0%.Conclusions: WB-DWI/MRI is highly accurate for diagnosis, staging and follow-up of patients with suspected gastric cancer. These results need to be confirmed in larger studies.