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

Abstract

Extramural venous invasion (EMVI) refers to the presence of cancer cells/tissue within the veins beyond the muscularis propria of the rectal wall. EMVI is regarded as a bad prognostic indicator in terms of local recurrence, distant metastasis, as well as overall patient survival. 1 In patients with rectal cancer, EMVI can provide a pathway for hematogenous dissemination of tumor cells, and is an independent risk factor for synchronous metastasis. 1,2 Moreover, EMVI, which is detected on MRI, is assumed to be helpful in predicting disease relapse. 2-4

Evaluation of Extramural Venous Invasion by Diffusion-Weighted Magnetic Resonance Imaging and Computed Tomography in Rectal Adenocarcinoma

“…In this study, patients enrolled in the EMVI (+) group had intermediate or definite tumour signal intensity within slightly or obviously enlarged veins and they were determined to be definitely positive mrEMVI patients according to the classification established by Chand et al Although prior literature has emphasized that, the addition of DWI to T2-weighted images contributes no further value in the diagnosis of EMVI, we think that lower ADC values may contribute to the diagnosis of EMVI evaluated with T2-weighted images. In support to this claim, Ahn et al demonstrate that when DWI and T2-weighted images are evaluated together, DWI decreases false negative results and increases reliability of EMVI diagnosed on T2-weighted images [9].…”

“…Lymph node involvement is usually in nodular configuration and EMVI can be distinguished by the visualization course of the vein, which proximally continues with the signal void tubular structure. Furthermore, the subserosal extension of tumour without perirectal vein invasion, desmoplastic reaction, or obliteration of signal void in perirectal veins on T2-weighted images are all other potential sources of false positive results on the MRI imaging [9,33]. In this study, patients enrolled in the EMVI (+) group had intermediate or definite tumour signal intensity within slightly or obviously enlarged veins and they were determined to be definitely positive mrEMVI patients according to the classification established by Chand et al Although prior literature has emphasized that, the addition of DWI to T2-weighted images contributes no further value in the diagnosis of EMVI, we think that lower ADC values may contribute to the diagnosis of EMVI evaluated with T2-weighted images.…”

“…Evaluating EMVI on MRI is challenging and most false positive diagnoses are related to tumour in lymphatics [9,10,33]. This is probably due to limited resolution of MRI scanners.…”

“…EMVI is defined as the presence of cancer cells in blood vessels beyond the muscularis propria and can be evaluated on MRI [6,7]. Upholding histopathological results as the gold standard, it has been shown that MRI has a specificity as high as 96% in the discrimination of EMVI and an accuracy rate of 70%–80% [8,9] particularly in using T2-weighted images. Vessel expansion, disruption of vessel borders, an irregular or nodular configuration of the vessel, and tumour signal intensity within the vein all constitute convincing evidence of EMVI on MRI.…”

“…The diffusion-weighted imaging (DWI) sequence is routinely performed in daily MRI scanning due to its superiority in tumour detection, characterization, and monitoring of tumour response in rectal cancers [9,10]. Some authors indicate that the DWI sequence does not have a major contribution in the detection of EMVI due to its low signal-to-noise ratio and suppression of signals, which lead to difficulty in detecting intermediate or high signal intensities of the tumour within the invaded venous structure on DWI [9,11]. However, limited literature has been published on the diffusion characteristics of rectal adenocarcinoma and the modification of the rectum's major drainage veins in patients with EMVI.…”