Regional lymph node status after neoadjuvant chemoradiation of rectal cancer producing a complete or near complete rectal wall response

Transanal excision of the tumour site after complete response to chemoradiotherapy can determine the rectal wall response to treatment. This study was designed to assess whether the absence of tumour in the rectal wall corresponds to the absence of tumour in the mesorectum (true pathological complete response).A retrospective review identified patients who underwent preoperative chemoradiation therapy for advanced mid and low rectal cancer followed by routine pre-planned radical surgery with total mesorectal excision. Patients in whom the pathology specimen showed no residual tumour in the rectal wall (ypT0) or a ypT1 lesion were assessed for tumour involvement in the mesorectum.Seventy-eight patients who underwent pelvic chemoradiation followed by radical surgery were reviewed. The rectal wall tumour disappeared in eight (ypT0). Of these, residual tumour was found in the mesorectum (ypT0N1) in one (12%) patient. Eleven patients were found to have ypT1 residual tumour. Of these, two (18%) had a final post-surgical staging of ypT1N1.Complete rectal wall tumour eradication was achieved in 10% of the patients, and downstaging to ypT1 was achieved in 14%. In 15% (12% in ypT0 and 18% in ypT1) of these patients, residual tumour cells were evident in the mesorectum. This would probably have rendered these patients with residual disease had a nonradical approach of transanal excision of the original tumour site been employed. Caution should be taken when considering the avoidance of radical surgery.