Target number of subjects and calculation basis This study aims to show that the tailored treatment based on intraoperative local excision/biopsy is not oncologically inferior to total mesorectal excision. The 5-year overall survival rate expected from the existing standard treatment was 85% (van der Valk. 2018, Rullier. 2020). The non-inferior margin of the customized treatment was 10%, type 1 error 0.10, power 80%, 1:1 ratio. When calculated with a 10% dropout rate, a total of 346 people, 173 in each group, needs to be recruited.~Study Subject Recruitment Plan~Selection and enrollment of subjects: Subjects in clinical trials must be enrolled by the investigator before starting surgical treatment.~Document consent: To the patient who is considered to be able to participate in the clinical trial as a subject, an oral explanation of this clinical trial will be presented to the participants, and the written consent to participate in the clinical trial shall be obtained.~Preoperative evaluation A pre-treatment examination to determine the selection of subjects and their underlying condition will be conducted. Pre-treatment examination will be performed to review whether the subject meets the selection and exclusion criteria, and subjects with significant abnormalities will be excluded.~Control group setting and randomization method Tailored treatment based on local excision and total mesorectal excision are randomly assigned 1:1 by web-based random number table (REDCap).~Statistical Analysis The statistical analyses will be conducted using intention-to-treat, and per-protocol approaches. Multiple imputation for missing covariates will be performed to determine whether there are systematic differences in terms of missing data. Analyses of the primary and secondary outcomes will be adjusted for potential co-variates.~Results of the quality of life and sexual/urinary function questionnaires will be compared using linear generalized estimating equations (GEE), adjusted for baseline values, the time effect, and the interaction effect between time and treatment.~Clinical and pathological variables will be compared using χ2 tests or Fisher's exact test for categorical variables, or with Student's t-test for continuous variables. Disease-free survival, relapse-free survival, and overall survival curves will be plotted using the Kaplan-Meier method, and differences in survival curves will be compared using the log-rank test. Multivariable analyses using the Cox regression hazard model will be conducted to identify the factors that are independently associated with disease-free survival, relapse-free survival, and overall survival. All statistical tests will be two-sided and values of p<0·05 will be considered statistically significant.
The purpose of this study is to show that tailored treatment based on local excision can expand the target of non-radical treatment in ycT2-3N0M0 patients after neoadjuvant chemoradiotherapy for low rectal cancer and that the oncologic safety is not inferior to that of total mesorectal excision.