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Complete Response after Neoadjuvant Therapy in Rectal Cancer: To Operate or Not to Operate?

Background/Aims: Evidence exists to support both surgical and nonoperative observational approaches to the management of patients with distal rectal cancer who achieve a complete response following neoadjuvant chemoradiotherapy (CRT). This article summarizes findings from key studies on management strategies for complete pathologic and clinical responders after neoadjuvant CRT for rectal cancer. Methods: A comprehensive literature review was undertaken comparing complete responders to neoadjuvant CRT who underwent surgical procedures or nonoperative observation. Results: The sensitivity and specificity of clinical assessment tools following neoadjuvant CRT are generally low. Endoscopic ultrasound and MRI are widely used for rectal cancer staging; PET/CT is applied for detecting residual cancer, although limitations exist in assessing mesorectal disease. In patients with rectal cancer who receive neoadjuvant CRT, rates of complete pathologic response vary from 5 to 44%. Rates of nodal disease in patients with complete pathologic response vary from 0 to 15%. In patients with stage 0 rectal cancer, excellent long-term oncologic results have been reported for both surgical resection and nonoperative observation; therefore, some authors consider that surgical resection may result in unnecessary morbidity. Whereas neoadjuvant CRT followed by total mesorectal excision (TME) reduces local recurrence and improves 5-year survival, TME is associated with significant morbidity and suboptimal functional results. Conclusion: Informed consent in patients with distal rectal cancer who achieve a complete response to neoadjuvant CRT must address both the potential risks of recurrence following nonoperative observation and the increased risks of postoperative morbidity and compromised function following extirpative surgery.