Added value of diffusion-weighted imaging for evaluation of extramural venous invasion in patients with primary rectal cancer

Objective: To evaluate the added value of diffusion-weighted imaging (DWI) to T-2 weighted imaging (T2WI) for detection of extramural venous invasion (EMVI) in patients with primary rectal cancer. Methods: 79 patients (50 men, 29 females, mean age 67.4 years, range 37-87 years) who had undergone rectal MRI and subsequently received surgical resection were included. The rectal MRI consisted of T2WI in three planes and axial DWI (b-values, 0, 1000 s mm(-2)). Two radiologists blinded to the pathologic results independently reviewed the T2WI first, and then the combined T2WI and DWI 4 weeks later. They recorded their confidence scores for EMVI on a 5-point scale (0: definitely negative and 4: definitely positive). The diagnostic performance of each reading session for each reader was compared by pairwise comparison of receiver operating characteristic curves. The area under the ROC curve (AUC) was considered as the diagnostic performance. The result of a histopathological examination served as the reference standard for EMVI. Results: For both readers, the diagnostic performance was not significantly different between the two image sets (for reader 1, AUC, 0.828 and 0.825, p = 0.9426 and for reader 2, AUC, 0.723 and 0.726, p = 0.9244, respectively). Conclusion: There was no added value of DWI to T2WI for detection of EMVI in patients with primary rectal cancer. Advances in knowledge: High-resolution T2WI alone is sufficient to assess EMVI and a supplementary DWI has no added value in patients with primary rectal cancer.