Concordance in MRI and Pathology Diagnosis of Extranodal Tumour Deposits

Aims: To assess the concordance between MRI and pathological diagnosis of extranodal tumour deposits (ENTD) using MRI mapping to guide pathologists. Currently we diagnose ENTD on MRI in our unit but this diagnosis has not been prospectively validated against that of pathology. The fact that pathologists in the UK do not routinely use TNM 7 means ENTD are misclassified as lymph nodes (LN). Even when ENTD are seen, they may not be reported if LN are also involved as LN are seen as being the most important factor. We aim to establish the true frequency of ENTD by prospectively correlating MRI diagnosis of ENTD against pathology. If, as we suspect, the frequency of ENTD is far greater than 10% and approaching 40% this would have significant implications for staging classifications and oncological decision making in the MDT setting.

Methods:  This will be a prospective interventional, multi-centre study. Patients will be identified from multidisciplinary team meetings. All patients presenting with primary adenocarcinoma of the rectum and undergoing resectional surgery (with or without prior neo-adjuvant treatment) will be eligible for inclusion in the study. If ENTD are thought to be present, the final MRI prior to surgery will be used to map the location of deposits both pre-operatively, and in real time while the specimen is being cut up. Baseline characteristics, MRI and pathology results and operative details will be anonymised and recorded in a secure database.

Outcomes: The primary outcome will be concordance of MRI and pathology for the detection of ENTD. Secondary outcomes will be MRI and pathology detection of EMVI, LN status and T stage as well as overall and disease free survival.

The COMET trial is open for recruitment.

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