Oncologic Outcomes Associated with MRI-Detected Extramural Venous Invasion (mrEMVI) in Rectal Cancer: A Systematic Review and Meta-Analysis.

BACKGROUND The role of MRI-detected EMVI (mrEMVI) as a reliable prognostic factor in rectal cancer has been emphasized in recent years but this finding remains underreported by many institutions. OBJECTIVE This review aimed to demonstrate the importance of pre- and post-treatment MRI-detected EMVI as independent prognostic factors of adverse oncologic outcomes in patients undergoing neoadjuvant therapy followed by total mesorectal excision. METHODS This review was designed using the PRISMA guidelines. The following electronic databases were searched from January 2002 to January 2020: CENTRAL, Ovid MEDLINE, PubMed and Ovid Embase. Main outcomes included disease-free survival (DFS) and overall survival (OS). Other outcomes of interest comprised positive resection margin and synchronous metastases. RESULTS Seventeen studies involving a total of 3821 patients were included for data synthesis. For pre-neoadjuvant treatment mrEMVI, pooled hazard ratio (HR) estimate for DFS was 2.30 (95%CI 1.54-3.44) for higher recurrence in mrEMVI-positive patients. mrEMVI-positive patients were found to have a lower OS with a pooled HR of 1.68 (95%CI 1.27-2.22). Pooled risk ratio (RR) for synchronous metastasis was 4.11 (95%CI 2.80-6.02) for mrEMVI-positivity. For post-neoadjuvant treatment EMVI (ymrEMVI), positive status showed a lower DFS with a pooled HR of 2.04 (95%CI 1.55-2.69). RR of having a positive resection margin status was 2.95 (95%CI 1.75-4.98) for ymrEMVI-positive patients. CONCLUSION This review showed that oncologic outcomes are significantly worse for both pre- and post-neoadjuvant treatment mrEMVI-positive patients. MRI-detected EMVI should be consistently reported in rectal cancer staging and may provide guidance for the targeted use of additional systemic therapy.