This was a propensity-score matched observational analysis, comparing the oncological outcome of surgical resection vs watch and wait apporach for rectal cancer patients with a cCR.

Pathologically confirmed stage II/III rectal adenocarcinoma patients who received neoadjuvant chemoradiotherapy followed by a clinical complete response from the year 2010 to 2018 were included. Sequential subjects were identified from a prospective maintained database in the Sun Yat-sen University Cancer Center. Clinical experts on rectal cancer from other 5 regional medical centers in China were also invited to participate, and provided data of cCR patients. Standardized forms for data collection were sanded to researchers in each center. Patients received radical resection will constituted our surgery group. Those refused surgery constituted the observation group who went on with the watch and wait approach. A propensity-score matched observational analysis will be used to compare the oncological outcome of these two groups.

Inclusion Criteria:

• Pathologically confirmed stage II/III rectal adenocarcinoma patients who received neoadjuvant chemoradiotherapy followed by a clinical complete response

Exclusion Criteria:

• history of a second primary malignancy.

Pathologically confirmed stage II/III rectal adenocarcinoma patients who received neoadjuvant chemoradiotherapy followed by a clinical complete response were included and divided into two groups according to the treatment followed.