• Histologically confirmed invasive, well-moderately differentiated rectal adenocarcinoma, mismatch repair proficient.

• MRI stage cT1 not eligible for transanal surgery or cT2-T3a.

• cN0 stage based on pelvic MRI - including absence of radiographic evidence of mesorectal nodal metastasis, tumour deposits or extramural venous invasion (EMVI).

• M0 stage based on no evidence of metastatic disease by CT imaging of chest, abdomen and pelvis.

• Mid to low-lying tumour eligible for transanal excision in the opinion of the treating surgeon.

• Medically fit to undergo radical TME surgery as per treating surgeon's decision.

• Participant is able (i.e. sufficiently fluent) and willing to complete the quality of life questionnaires in either English or French or Spanish.

• Age of at least 18 years.

• No contraindications to protocol chemotherapy.

• Adequate normal organ and marrow function: ANC ≥ x 10\^9/L; platelet count ≥ 100 x 10\^9/L; bilirubin \< 1.5 UNL, excluding Gilbert's syndrome; Estimated creatinine clearance of ≥ 50ml/min

• Patient must have an ECOG performance of \<2 (or Karnofsty ≥ 60%).

• Must be accessible for treatment and follow-up

• Males and females of reproductive potential must have agreed to use a highly effective contraceptive method during and for 6 months after completion of chemotherapy.

• HIV-infected patients on effective anti-retroviral therapy with undetectable viral load within 6 months are eligible for this trial.