“Sigmoid take-off” to define recto-sigmoid junction and its impact on rectal cancer classification, staging, and management

Abstract

Aim

The primary objective of this study was to determine the clinical impact of using sigmoid take-off (STO) in the management of rectal cancer. We also evaluated the inter-observer reliability in the identification of STO.

Material and Methods

This retrospective study reviewed staging MRI of patients with mid and high-rectal cancers performed between January 2019 and December 2022. The location of the tumour was reclassified based on STO as defined by D'Souza et al. (2018) and compared with the location determined based on distance from the anal verge. The proportions of cases that show a change in tumour location from rectal cancer to sigmoid cancer and the potential change in treatment were noted. The interobserver agreement for the location of STO and the location of tumours from STO was studied among four subspecialised abdominal radiologists.

Results

Out of 134 rectal cancer patients included, STO-based assessment resulted in the reclassification of 13.4% (n=18) cases into sigmoid cancer. There was, however, no change in the stage of cancer. Among these 18 patients, there would have been a change in management in 5 patients had the initial assessment been a sigmoid cancer. There was excellent agreement among the radiologists for measuring the distance of STO from the anal verge (ICC = 0.883, p<0.001) and determining the location of the tumour based on STO (K = 0.82, p<0.001).

Conclusions

Using STO changed the location of tumours in 13.4% of high- and mid-rectal cancers. There was excellent agreement among radiologists regarding determining STO and identifying tumour locations using STO.