Restaging rectal cancer following neoadjuvant chemoradiotherapy

Table 1 Recommended tumour response schema for rectal cancer after neoadjuvant chemoradiotherapy

	cCR	ncCR	Poor response
DRE	No palpable tumour material present	Minor mucosal abnormalities	Palpable 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 fulfilled	Small 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 mandatory	Visible 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 nodes	Obvious 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 mm	Visible macroscopic tumour and/or lack of regression of involved lymph nodes; Cases who do not fulfill the criteria for either a cCR or ncCR

DRE: Digital rectal exam; cCR: Clinical complete response; ncCR: Near clinical complete response; MRI: Magnetic resonance imaging.

Table 2 Take-home message

Re-staging
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

CT: Computed tomography; ncCR: Near clinical complete response; MRI: Magnetic resonance imaging.