Rates of early rectal cancer detection are on the increase due to screening programmes and wider public awareness. Most rectal cancer is treated by radical surgery which carries significant short and long-term morbidity. However early cancers are often node-negative, so many could be cured by local excision.
Local excision is associated with lower perioperative morbidity, mortality, and a quicker recovery. It preserves the rectum and anal sphincters so retains normal bowel function and avoids the risk of impaired urinary and sexual function. These factors result in better quality of life for the patient compared with radical surgery as well as lower healthcare costs. These benefits, however, need to be balanced against the possible oncological compromise and risk of leaving behind positive lymph nodes. While radical surgery, which removes the mesorectal lymph nodes, has higher morbidity and mortality, the local recurrence rate is <5% and survival rates are high. Yet when balancing quality of life with long-term survival, the patient’s and surgeon’s opinions may differ.
Traditionally, local excision has meant open transanal excision but the limited access usually resulted in a limited quality of specimen. In 1983, Buess et al.1 introduced transanal endoscopic microsurgery. The specialised instrumentation provided optimal visualisation, a stable pneumorectum, and access as far as the rectosigmoid junction. Even so, uptake among colorectal surgeons was initially slow. The inception of TAMIS (Transanal Minimally Invasive Surgery),2 where a multi-channel access device originally designed to enable single-incision laparoscopic surgery is used transanally, has led to a rapid growth and uptake of local excision for rectal cancer.
Early reports of outcome after local excision of rectal cancer showed unacceptably high rates of local recurrence, even among T1 tumours. However, for a subset of tumours, those which were small, well-differentiated, with no lymphatic of vascular invasion, and which were completely excised, local recurrence rates equivalent to those after radical resection were achieved. Therefore, selecting appropriate patients for local excision requires careful preoperative assessment of the tumour clinically, endoscopically, and with high-resolution magnetic resonance imaging (MRI) to assess tissue planes and lymph nodes. A further consideration is whether local excision will compromise later radical surgery should it become necessary, either because of unexpected adverse histopathological features in the locally excised tumour, or as a salvage procedure in the case of local recurrence. Following local excision, meticulous histopathological assessment detailing the size and depth of the tumour, degree of differentiation, lymphatic and vascular invasion, and tumour budding is essential to detect higher-risk tumours which are associated with an increased risk of positive lymph nodes. If these features are found, completion radical surgery would generally be advised to reduce the risk of local recurrence.
Other options to mitigate the risk of local recurrence are close surveillance and radiotherapy. Indeed, several trials are now exploring how surveillance and pre or postoperative radiotherapy can extend the range of tumour size and stage that can safely be removed by local excision, permitting more patients to benefit from rectal preservation. However, the advent of these novel approaches demands a robust framework to ensure that they are introduced safely and do not expose patients to the risk of an oncologically inadequate removal of rectal cancer.