RECTAL TUMOR STAGING MRI; HOW EFFECTIVE IS IT IN CHARACTERIZATION OF DEPTH OF EXTRAMURAL INVASION AND EXTRAMURAL VASCULAR INVASION?.

Abstract

Introduction:

Rectal cancer is amongst the most common gastrointestinal tumors. MRI is required at diagnosis followed by with or without neoadjuvant therapy and surgery. Accurate staging is not only important for predicting prognosis but also determine the risk of recurrence. Independent prognostic factors like extramural invasion (EMI) into mesorectal fat, extramural vascular invasion (EMVI) and circumfrential resection margins are also very important and needs to be addressed in MRI reports as presence of any of these factors may change the management plan entirely.

Objective: The purpose of this study is to determine accuracy of baseline MRI in detecting extramural tumor extension and extramural vascular invasion in rectal tumors taking pathological staging as gold standard.

Materials and Methods:

The study was approved by our institutional review board which waived the requirement for informed consent. The clinical data of all the patients treated for rectal carcinoma at Shaukat Khanum Memorial Cancer Hospital and Research Center, Lahore between 1^st December 2015 and 30^th November 2017 were retrospectively evaluated for the presence of EMI and EMVI by rectal carcinoma on MRI. EMVI was then graded over 5 point scale. Findings of MRI were then correlated with histological findings and were labelled as positive or negative on the basis of per-operative presence or absence of EMI and EMVI.

Results:

117 patients were included in this study. Out of these 117; 111 patients (94.9 %) received pre-operative chemoradiotherapy. 6 patients (5.1%) did not receive pre-operative chemotherapy and underwent upfront surgery. On MRI EMVI (mr-EMVI) was present in 22(18.8%) patients while on pathology it was present in 19 (16.2%) patients. A close association was observed between the baseline mr-EMVI status and the extent of mesorectal invasion. Stage T3c tumors were the most frequent to present EMVI i.e. 54.5% (12/22). On baseline MRI mr-EMVI was predominantly present in tumors located in mid rectum (86.4%; 19/22). EMI was also seen frequently in stage T3c patients (i-e 45/117;38.5%). Overall MRI has accuracy in T3 disease was found to be 76.14 %

Conclusion:

Baseline MRI is highly effective imaging modality to evaluate pre-operative EMI and EMVI in rectal cancers which have a significant independent impact on the management plan.

Keywords: Rectal cancer, Extramural invasion, Extramural vascular invasion, MRI.