Standard laparoscopic low anterior resection versus transanal TME for rectal carcinoma. Comparing the extend and completeness of mesorectal excision evaluated by magnetic resonance imaging*

Worldwide, colorectal cancer is the third most common malignancy in males and
second most common malignancy in females. Approximately 33% of this tumors is
localized in the rectum. The standard potential curative treatment for rectal
cancer is surgery. In 1978, Heald accomplished a new approach calling the total
mesorectal excision (TME) at that time performed by extensive laparotomy. Over
the years surgery has evolved and nowadays laparoscopic TME is the golden
standard for rectal cancer surgery. Although short term benefits after
laparoscopic surgery have been shown, oncological quality and survival rates
don*t seem to improve. TME surgery can thereby still be improved and challenges
during rectal dissection remain.
Rectal surgery is considered difficult because of poor visualization of the
distal part of the rectum, especially in male and obese patients. By performing
a transanal TME (TaTME) the rectum is approached transanally and these
disadvantages are of lesser influence. The rectum is herewith mobilized under
direct endoscopic visualization beginning at the most distal margin of the
mesorectum, working upwards. Although no randomized trials have been published,
described advantages of TaTME are better visualization of the distal part of
the rectum, complete mesorectal excision and improved specimen.
Because of this advantages, we hypothesize that after TaTME, less residual
mesorectum will be found on postoperative MRI comparing to laparoscopic
approach, which could imply a decreased risk of recurrence.

This study, comparing two cohorts, is designed to determine the postoperative
residual mesorectum on MRI after TME. Patients with a clinical T1-3 rectal
carcinoma (10cm or less from the anal verge based on preoperative MRI of the
pelvis) who underwent TaTME with curative intent are included. A corresponding
group of patients who underwent laparoscopic TME in The Gelderse Vallei
Hospital will be compared in terms of localization and amount of residual
mesorectum.

This study, comparing two cohorts, is designed to determine the postoperative
residual mesorectum on MRI after TME. Patients with a clinical T1-3 rectal
carcinoma (10cm or less from the anal verge based on preoperative MRI of the
pelvis) for whom a laparoscopic or transanal TME with curative intent was
performed. Patients who were operated in 2011 till 2013 in The Gelderse Vallei
Hospital were operated through laparoscopic approach. Patients in 2013 to 2015
underwent transanal TME, and will be included starting with the most recent and
working backwards until the amount of patients calculated are included.

Patients who underwent a laparoscopic TME will get magnetic resonance imaging
to determine postoperative residual mesorectum. Patients who underwent a
transanal TME already got a postoperative MRI according to protocol.
No significant biological effects are associated with conventional MR imaging.
Therefore, the estimated risk for study objects is classified as *negligible
risk* (Dutch: verwaarloosbaar risico).