Can pathological complete response in the primary tumour following pre-operative pelvic chemoradiotherapy for T3-T4 rectal cancer predict for sterilisation of pelvic lymph nodes, a low risk of local recurrence and the appropriateness of local excision?

Introduction: Local excisionis considered inappropriatetreatment for T3–T4 rectal adenocarcinomas,as it cannot provide prognosticinformation regarding lymphnode involvement and has a high riskof pelvic recurrence. Preoperativechemoradiation (CRT) studies inrectal cancer suggest that a pathologicalcomplete response (pCR) in theprimary tumour provides an excellentlong-term outcome. If downstaging tostage pT0 predicts a tumour responsewithin the perirectal and pelvic lymphnodes, this may allow local excision tobe performed without increased risk ofpelvic recurrence. This retrospectivestudy aimed to determine the incidenceof involved lymph nodes followingpCR (ypT0) after preoperative CRTand total mesorectal excision.Method: The outcome and treatmentdetails of 211 patients undergoingpreoperative CRT for clinically stagedT3–T4 unresectable rectal adenocarcinomasbetween 1993 and 2003 atMount Vernon Hospital were reviewed.Results: Data were recordedfrom the 143 patients who completedtreatment with a median follow-up of25 months. Twenty-three patients(18%) were found to have had a pCR.Four out of 23 patients (17%) hadinvolved lymph nodes. No pelvicrecurrences developed after a ypCR.Overall survival was similar for patientswith ypT0 or residual tumour.Conclusion: Pathological completeresponse in the primary tumour failedto predict a response in the perirectallymph nodes (p=0.08). The degree ofresponse predicted a lymph node response(p=0.02). The detection ofypCR identified patients with a lowrate of pelvic recurrence. This may inthe future allow selection of patientsfor whom local excision can beperformed without a higher risk oflocal relapse.