Endoscopic (EID) Versus Surgical (TAMIS) Local Excision for Early Stage Rectal Cancer

In this clinical trial, we compare the endoscopic technique, endoscopic intermuscular dissection (EID), with the surgical technique, transanal minimally invasive surgery (TAMIS) for the treatment of early stage rectal cancer. The aim of this study is to investigate whether one of them leads to better outcomes. Researchers will focus particularly on: * How effectively each technique completely removes the cancer * How quickly patients recover after treatment and whether complications occur * Outcomes after three years (does the cancer go away, or does it come back?) * The impact of both techniques on bowel function and quality of life Participants will: * Be randomly assigned to receive either surgical or endoscopic treatment for their rectal cancer * Keep a diary twice a day to record pain symptoms and recovery during the first 30 days after treatment and complete questionnaires within a 3 year period * Visit the clinic for follow-up appointments within a 3 year period

Inclusion criteria: To be eligible to participate in this study, a patient must meet all of the following criteria: * Adult patients (≥ 18 years of age). * Suspected rectal D-SMIC based on optical diagnosis using narrow-band imaging: * Hiroshima C2/3, JNET 3, NICE III, Kudo Vn pit pattern. * The presence of non-lifting together with features of superficial submucosal invasion (Hiroshima C1, JNET 2B, Kudo Vi pit pattern). * MRI shows cT1-T2 invasion and minimum of 1 mm preserved muscularis propria. * Tumour with its lower border situated on or below the level of the sigmoid take off as shown on rectal MRI. * Staging rectal MRI confirms absence of suspicious malignant mesorectal lymph nodes, defined as mucinous lymph nodes, perirectal lymph nodes \>9 mm in short-axis diameter, or ≥7 mm for lateral lymph nodes (classified as certain cN+), or 5-9 mm peri-rectal lymph nodes with at least 2 suspect morphological features: round shape, heterogeneity and/or irregular borders (classified as doubtful cN+). * Staging rectal MRI confirms absence of tumour deposits. * Staging rectal MRI confirms absence of extramural vascular invasion (EMVI). Exclusion criteria: A patient who meets one or more of the following criteria will be excluded from participation in this study: * Lesions involving more than 50% of the circumference. * Total lesion size larger than 6 cm. * Prior endoscopic or surgical resection attempts of the tumour. * Recurrent cancer after previous surgical or endoscopic local resection. * Severe pre-existing faecal incontinence with impaired quality of life. * Inflammatory bowel disease (IBD) with previous inflammation of the rectum. * Previous pelvic irradiation or neoadjuvant therapy. * Poor general health that prevents the use of general anaesthesia. * Inability or contraindication to undergo MRI scan. * Concomitant malignancies or other severe medical conditions that, in the opinion of the multidisciplinary team (MDT), are likely to result in death within 5 years. * AJCC stage II, III or IV CRC within the last 5 years or synchronous CRC. * Inability to complete questionnaires or sign informed consent. * Known pregnancy.