Added value of apparent diffusion coefficient in the preoperative MRI staging of gastric cancer: comparison with postoperative histology

Purpose: To investigate the influence of ADC in the diagnostic performance of MRI in the preoperative staging of gastric cancer. Methods a nd Materials: Between October 2009 and October 2014 a total of 88 patients with biopsy -proved gastric cancer underwent 1.5 T MRI with T1, T2 and DWI sequences and then treated with radical surgery. Two radiologists independently measured minimum ADC from tumour and assessed T and N staging by MRI. All findings were then compared with final histology, considering T1- 3 vs T4a -b and N0 vs N+ (according to 7th TNM staging). Results: Minimum pathological ADC was significantly different both for T and N staging ( p < 0.01). An optimal cut -off of 1.28 x 10 -3 mm2/s could distinguish between patients with local invasion (area under the curve: 0.91; p < 0.001). For T staging, MR showed a sensitivity of 70% and a specificity of 68%, which increased to 87% and 88% respectively, when adding our ADC cut -off. For N staging, the sensitivity increased from 68% to 77% with similar results in terms of accuracy (69% and 70%, respectively), when adding our ADC cut -off. Conclusion: ADC is different according to local invasion and nodal involvement in gastric cancer. Adding ADC to morphological T and N staging by MRI helps in the prediction of postoperative staging.