What to Do After Surgery for Localised Rectal Cancer in the Upper Third of the Rectum (MMRp/MSS)
This protocol covers adjuvant management for patients with localised rectal cancer sited in the upper third of the rectum and confirmed mismatch repair proficient (MMRp) / microsatellite stable (MSS) status, following surgical resection.
Clinical Scenario
Localised rectal cancer located in the upper third of the rectum, mismatch repair proficient (MMRp) / microsatellite stable (MSS). For tumours at this site, the benefit of radiotherapy is very limited, and management follows an approach analogous to that used for colon carcinoma.
After Surgical Resection
The prior treatment step was surgical resection — partial mesorectal excision (PME) or total mesorectal excision (TME). The target of surgery was microscopically complete (R0) resection with a clear circumferential resection margin (tumour >1 mm from the CRM). When specific post-operative pathological findings are identified — or when that resection margin goal was not secured — further treatment becomes necessary, and this protocol defines that next step.
Treatment Approach
Following surgery, adjuvant chemotherapy is considered based on clinical risk assessment. In certain post-operative situations, adjuvant chemoradiotherapy may additionally be indicated. The complete eligibility criteria, sequencing, and regimen details are available in the full protocol.
References
DOI: 10.1016/j.annonc.2025.05.528
For carcinomas in the upper third of the rectum, the benefit of RT is very limited; therefore, a procedure analogous to the approach for colon carcinoma may be preferred.
Algorithms for the management of localised rectal cancer in the upper third of the rectum are shown in Figures 1 and 2.
Adjuvant ChT with a fluoropyrimidine and (potentially) oxaliplatin should be offered (according to clinical risk assessment) following PME or TME alone [I, A].
In patients who did not receive preoperative RT, adjuvant CRT should be offered in case of CRM positivity, pT4b, pN2 with extracapsular spread close to the MRF or poor-quality TME [III, A].
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