Objective: We performed a retrospective review to identify objective factors that could facilitate the surgeon's decision regarding the feasibility of an adequate resection with a margin of< 2 cm from the dentate line. We could not find clear guidelines for clinicians regarding the use of close margins for sphincter saving surgery following chemoradiation (CRX). We proposed what state of the art imaging tools are potentially useful to identify tumor downstage following preoperative CRX and aid in the development of guidelines.
Methods: Reviewed of the literature on the subject and performance of current diagnostic imaging studies useful in identifying rectal tumor downstaging after preoperative CRX.
Results: Without safe margins of resection an abdominoperineal resection (APR) is the operation of choice. All sphincter saving rectal cancer operations results for ultra-low tumors need to be as good as results from an APR. Performing frozen section for the ultralow rectal cancer margins is recommended. The Endorectal Ultrasonography (ERUS) data appear encouraging and suggest that we should evaluate TRUS earlier after CRX, before the desmoplastic reaction and scar tissue appears. It could turn out to be an objective and accurate method of evaluating tumor downstaging. Color Doppler evaluation has shown higher specificity than that of grey scale ultrasound in staging and differentiating scar from anal cancers. Similarly, PET scanning performed earlier and with modern PET-CT equipment is worth exploring.
Conclusion: At this point with the information available from the literature, we suggest that patients with clinically advanced rectal cancer can have a distal margin resection of less than 2 cm if: 1- the tumor is not mucin producing, 2- the tumor is not high-grade, and 3- the response to preop CRX is adequate, however there exist no clear guidelines available to judge what is an excellent versus a moderate or poor response.