Application of Circulating Tumor DNA Test in the Diagnosis and Treatment of Patients With Advanced Rectal Cancer

Inclusion Criteria: * Histologically or cytologically confirmed primary rectal cancer； * First treatment； * 18 years of age or older, male or female； * According to the indications of operation, surgical treatment can be carried out； * According to the indications of radiotherapy, radiotherapy can be carried out； * The physical status score of ECOG was 0\~1； * Organ function is appropriate; * Expected survival time more than 3 months； * During the treatment period and 6 months after treatment, contraception was not in lactation； * The patient volunteered and signed the informed consent. Exclusion Criteria: * Poor compliance and failure to receive medication or follow up according to plan； * There are other serious violations of the programme; * At present, it has been included in other clinical trials, or at the same time, it has been included in other medical research which is judged to be incompatible with this research； * It has a history of other cancers. Unless the cancer is completely relieved, the disease is not treated for more than 3 years.