Introduction
The aim of this study was to research whether imaging could improve the outcomes of sigmoid colon cancer treatment, by better pre-operative staging and consistent differentiation of the rectum from the sigmoid.
Methods
I investigated sigmoid cancer outcomes by systematic review and meta-analysis. I performed a literature search and evidence synthesis on definitions of the rectum, and compared their accuracy in a radiological study. I led a Delphi consensus to agree a definition of the rectum international with colorectal experts. I designed a prospective, ethics-approved joint radiological-tissue study to both investigate the concept of a sigmoid mesenteric waist and validate an imaging-based definition of the rectum. I created and analysed a multi-institutional database to identify prognostic variables for colon cancer and compare Computed Tomography (CT) staging systems.
Results
The pooled local recurrence rate for sigmoid cancer on meta-analysis is high at 10.5%. A wide range of definitions of the rectum are employed by national associations and guidelines. In-vivo radiological comparison of all definitions confirmed they did not accurately localise tumours. Through a Delphi consensus of 132 international experts, the imaging landmark of the sigmoid take-off was agreed to define the rectum. A mesenteric waist was identified at the rectosigmoid junction that could serve as a pathological definition of the rectum. Radiological and specimen analysis validated the sigmoid take-off on imaging as a definition of the rectum.
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In 414 patients the local recurrence rate of sigmoid cancer remained high at 12.6%, and was associated with CT-disease features. Identification of tumour deposits and extramural venous invasion on CT were associated with higher rates of recurrence than TNM or T3 substage based CT-systems.
Conclusion
There are a wide range of non-anatomical definitions of the rectum currently in use, which cannot accurately localize tumours. An international Delphi consensus definition of the rectum was the sigmoid take-off, which was validated on specimen analysis. Local recurrence of sigmoid cancer is unexpectedly high. Pre-operative imaging can identify patients that are at higher risk of recurrence.