Transanal Total Mesorectal Excision (TaTME) and Quality of Rectal Cancer Surgery: Do we Really Know?
In recent months, there have been numerous publications from many countries discussing the potential role of transanal total mesorectal excision (TaTME) for the removal of the rectum. While this new technical approach to a challenging operation has been used for a range of indications—both benign and malignant disease, for example—it is in the management of rectal cancer that the major interest lies. The recent correspondence from China follows a series of publications in this journal and is worthy of consideration.
The concept of total mesorectal excision (TME) for rectal cancer, first introduced by Heald, has proven to decrease the rate of local cancer recurrence. Herald's original concept was based on the fact that local recurrence is mainly a result of isolated distal mesorectal deposits. Therefore, to decrease the rate of local recurrence, the removal of the distal mesorectal tongue is essential. The TME technique involves meticulous and sharp dissection of the entire mesorectum along the avascular planes outside the perirectal fascia. The dissection of mesorectum continues to the level of anorectal junction, where, of course, the bulk of mesorectal tissue decreases. In the original study, this technique was recommended for all rectal cancers.1 However, further studies of mesorectal tumor deposits showed that the prevalence of distal deposits is too low to justify the concept of TME for all rectal cancers. Moreover, excising the mesorectum to the level of levators will result in a large numbers of very low pelvic anastomosis with higher anastomotic leak rates and worse functional outcome. Therefore, the classic TME is now performed mainly for distal mid and low rectal cancers. A tumor-specific mesorectal excision with a 5-cm distal resection margin for high rectal tumors is believed to be oncologically adequate.
The quality of rectal cancer surgery in the modern era is based on 3 main factors—distal resection margin, circumferential resection margin, and mesorectal grade and lymph node yield. In this context, the main value of a TME may well be attributed to maintaining a clear circumferential resection margin and a high mesorectal grade, rather than purely excising the very distal mesorectal tongue.
Transanal total mesorectal excision has gained popularity over the past few years in the surgical management of rectal cancer. Conventional TME remains a challenging operation in obese patients with a narrow pelvis. Distal rectal dissection and cross-stapling of the distal rectum remains technically difficult in the conventional TME, especially when performed laparoscopically or robotically due to the limitations of instrument technology. The concept of starting the dissection from the bottom up can potentially solve some of these problems. In particular, the use of minimally invasive platforms can potentially increase the precision of the distal resection margin from the beginning of the procedure and eliminate the need for cross-stapling the rectum in a narrow pelvis. In addition, the anterior dissection, which has the potential of damage to urethra, prostate, seminal vesicles, or vagina, can be facilitated by a transanal approach. Review of the published series attests to the high quality of resection that can be achieved by a TaTME approach (Table 1). This is comparable with the quality of resection reported in large trials of conventional top-to-bottom approach.13 Data regarding clinical follow-up and long-term local recurrence after transanal TME are not yet available. Nevertheless, using quality of resection as a surrogate marker of local recurrence keeps TaTME a very promising and exciting technique in the surgical management of low to mid-rectal cancers.