Low presence of intraluminal cancer cells in rectal washout during transanal total mesorectal excision.
21 August 2021
Read paperLocal recurrence (LR) after rectal cancer surgery is a disastrous event occurring in up to 10% after transanal total mesorectal excision (TaTME) 1-3. LR usually arises within two years of primary surgery and is associated with significant morbidity 4. The adoption of total mesorectal excision (TME) has dramatically improved LR rates 5, although some studies have indicated early multifocal pelvic LR after TaTME 6, 7. Factors associated with LR are mainly related to non-radical surgery, intraoperative bowel perforation, and TNM stage 8-10. Another potential risk factor is the direct implantation of viable intraluminal cancer cells in the peri-anastomotic area 11-13. Different technical aspects, including rectal washout to eradicate free intraluminal cancer cells, may be important to achieve the best possible outcomes 14-18.
In recent years, TaTME was introduced as “a new solution to some old problems” 19. The procedure allows for precise visualisation of the operative field in the lowermost part of the pelvis 20. Rectal washout is an integrated part of TaTME. However, details about the procedure including the appropriate fluid type and volume, are not standardised 12.
Our recent pilot study examined fluid samples from rectal washout to determine the appropriate fluid volume needed to eliminate intraluminal cancer cells during TaTME. We hypothesised that since rectal washout during TaTME is performed after the placement of a snog purse-string suture without touching the tumour, it has a lower yield of cancer cells than rectal washout in normal TME dissection.
The study was performed at Slagelse Hospital, Denmark from March 2020 to January 2021. We included 21 patients treated with TaTME for rectal cancer. After the placement of a purse-string suture, intraoperative rectal washout was performed with five portions of 100 ml of sterile water. After each portion, a fluid sample was collected by instilling 50 ml of saline. A sixth sample was obtained from the presacral space following the retrieval of the specimen. Cellblocks were created from the fluid samples which were labelled either “cancer cells” positive or “cancer cells” negative by our gastrointestinal pathologist.
Details about patient characteristics can be read in our published research letter in the BJS. In summary, the washout samples were positive in only three of the 21 included patients. However, after 500 ml of rectal washout, all fluid samples were negative. In none of the included 21 patients, cancer cells were found in the presacral cavity following specimen extraction, indicating that TaTME carries minimal risk of intraabdominal wound contamination with cancer cells.
To conclude, although it seems like intraluminal cancer cells are rare after rectal washout in TaTME for rectal cancer, 500 ml of rectal washout is probably needed to ensure adequate elimination of intraluminal cancer cells.
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