AIM:To evaluate the long-term results of conventional chemoradiotherapy and laparoscopic mesorectal excision in rectal adenocarcinoma patients without adjuvant therapy.METHODS:Patients with biopsy-proven adenocarcinoma of the rectum staged cT3-T4 by endoscopic ultrasound or magnetic resonance imaging received neoadjuvant continuous infusion of 5-fluorouracil for five weeks and concomitant radiotherapy.Laparoscopic surgery was planned after 5-8 wk.Patients diagnosed with ypT0N0 stage cancer were not treated with adjuvant therapy according to the protocol.Patients with ypT1-2N0 or ypT3-4 or N+were offered 5-fluorouracil-based adjuvant treatment on an individual basis.An external cohort was used as a reference for the findings.RESULTS:One hundred and seventy six patients were treated with induction chemoradiotherapy and 170underwent total mesorectal excision.Cancer staging of ypT0N0 was achieved in 26/170(15.3%)patients.After a median follow-up of 58.3 mo,patients withypT0N0 had five-year disease-free and overall survival rates of 96%(95%CI:77-99)and 100%,respectively.We provide evidence about the natural history of patients with localized rectal cancer achieving a complete response after preoperative chemoradiation.The inherent good prognosis of these patients will have implications for clinical trial design and care of patients.CONCLUSION:Withholding adjuvant chemotherapy after complete response following standard neoadjuvant chemoradiotherapy and laparoscopic mesorectal excision might be safe within an experienced multidisciplinary team. AIM: To evaluate the long-term results of conventional chemoradiotherapy and laparoscopic mesorectal excision in rectal adenocarcinoma patients without adjuvant therapy. METHODS: Patients with biopsy-proven adenocarcinoma of the rectum staged cT3-T4 by endoscopic ultrasound or magnetic resonance imaging received neoadjuvant continuous infusion of 5-fluorouracil for five weeks and concomitant radiotherapy. Laparoscopic surgery was planned after 5-8 wk. Patient diagnosed with ypT0N0 stage cancer were not treated with adjuvant therapy according to the protocol. Pats with ypT1-2N0 or ypT3-4 or N + were offered 5-fluorouracil-based adjuvant treatment on an individual basis. An external cohort was used as a reference for the findings. RESULTS: One hundred and seventy six patients were treated with induction chemoradiotherapy and 170 underwent total mesorectal excision. Cancer staging of ypT0N0 was achieved in 26/170 (15.3%) patients. After a median follow-up of 58.3 mo, patients withypT0N0 had five-year disease-free and overall survival rates of 96% (95% CI: 77-99) and 100%, respectively. We provide evidence about the natural history of patients with localized rectal cancer achieving a complete response after preoperative chemoradiation. The inherent good prognosis of these patients will have implications for clinical trial design and care of patients. CONCLUSION: Withholding adjuvant chemotherapy after complete response following standard neoadjuvant chemoradiotherapy and laparoscopic mesorectal excision might be safe within an experienced multidisciplinary team.