Opinion Review
Copyright ©The Author(s) 2023.
World J Gastrointest Oncol. May 15, 2023; 15(5): 700-712
Published online May 15, 2023. doi: 10.4251/wjgo.v15.i5.700
Table 1 Recommended tumour response schema for rectal cancer after neoadjuvant chemoradiotherapy

Poor response
DRE No palpable tumour material presentMinor mucosal abnormalitiesPalpable tumour mass; Cases who do not fulfill the criteria for either a cCR or ncCR
Endoscopy No residual tumour material or only a small residual erythematous ulcer or scar; Endoscopic biopsy not mandatory to define a cCR, biopsy should not be performed, especially if the DRE, rectoscopy and MRI criteria for a cCR are all fulfilledSmall and smooth regular irregularities including residual ulcer, or small mucosal nodules or minor mucosal abnormalities, with mild persisting erythema of the scar; Endoscopic biopsy not mandatoryVisible macroscopic tumour; Cases who do not fulfill the criteria for either a cCR or ncCR
MRI Substantial downsizing with no observable residual tumour material, or residual fibrosis only (with limited signal on diffusion weighted imaging), sometimes associated with residual wall thickening owing to oedema, no suspicious lymph nodesObvious downstaging with residual fibrosis but heterogeneous or irregular aspects and signal or regression of lymph nodes with no malignant enhancement features, but with a size > 5 mmVisible macroscopic tumour and/or lack of regression of involved lymph nodes; Cases who do not fulfill the criteria for either a cCR or ncCR
Table 2 Take-home message
Why It allows for the development of a tailored surgical treatment with the goal of avoiding poor oncological outcomes and overtreatment
When It remains unclear. Experts recommend: (1) For patients receiving neoadjuvant chemoradiotherapy or short-course radiotherapy, the 2-step approach, at 12 wk and 16-20 wk after starting treatment if organ preservation is a priority; (2) For patients receiving total neoadjuvant therapy, assessment at 20-38 wk after commencing treatment according to the duration of the treatment; and (3) In case of ncCR, a second assessment 3 mo later taking into account initial tumour stage and treatment approach, if organ preservation is a priority. There is insufficient evidence to recommend proper timing for the earlier identification of patients with a poor response before the conventional time. Nevertheless, experts advise caution and selective earlier imaging in patients with tumours featuring certain high-risk characteristics (such as advanced cT stage)
How Digital rectal examination, endoscopy and pelvic MRI for local tumour restaging; Chest and abdominal CT for distant disease. The current aim of local response assessment is not correct T-staging but the accurate differentiation between “good responders” (who are ypT0N0 or ypT1N0) and “poor responders.” In the latter, the risk of incomplete resection, such as MRF positivity, adjacent organ or anal sphincter infiltration, and residual lateral pelvic node involvement should also be identified