Prognostic factors of pelvic MRI at the initial workflow in locally advanced rectal cancer: Focus on extra mural venous invasion and tumour deposits

Abstract

Introduction: Tumour deposits (TD) and extramural venous invasion (EMVI) are key anatomopathology prognostic criteria in rectal cancer. According to the 2018 ESGAR recommendations, they should be included in every MRI report. The present study aimed at identifying pelvic MRI survival prognostic factors in locally advanced rectal cancers before neo-adjuvant treatment, with a focus on EMVI and TD (mrEMVI and mrTD).

Methods: Between 2010 and 2014, we conducted a retrospective study about 69 patients who underwent a pre-operative radiotherapy for a non-metastatic rectal cancer. All MR images were acquired on machines with a 1.5 or 3.0 Tesla field strength and were interpreted in compliance with the 2018 ESGAR recommendations.

Results: Out of the 27 patients who were mrEMVI+ (39.1%), MRF was involved in 77.7% of the cases vs. 33.3% for the mrEMVI- tumours. Fifteen (55.5%) out of the 27 mrEMVI+ tumours were mrTD+. This represents 21.7% of our population. mrEMVI/mrTD+ tumours were more RCT resistant, their downstaging happened in 6.7% of cases. In case of tumour downstaging, DFS increased significantly (P=0.02) unlike OS (P=0.2).

Discussion: The present study supports the fact that both mrEMVI and mrTD status are important pelvic MRI prognostic factors. Future studies could focus on relating mrTD tumours status to pathological results to define if post-RCT downstaging of TD has an impact on OS.

Keywords: EMVI; Pelvic MRI; Prognostic factors; Rectal cancer; Tumour deposits.