In this study, the investigators establish a model for predicting the efficacy of conversion therapy for the patients with unresectable liver metastases of colorectal cancer based on the detection of 5-hydroxymethylcytosine (5-hmC) in training group and validate the effectiveness of the model using a validation group.

Radical resection is the preferred treatment of colorectal cancer patients with liver metastasas which significantly reduce the survival. However, the majority of the patients cannot receive liver lesions resection resulting from the size, number and bad location. Conversion therapy can improve the resection rate of these patients. Unfortunately, the efficacy of conversion therapy is still poor in part of the patients. So, it is crucial to distinguish the beneficial ones from the others.

The aim of this single center study is to establish a model for predicting the efficacy of conversion therapy for the patients with unresectable liver metastases of colorectal cancer based on the detection of 5-hmC. Patients will be eligible for inclusion if they suffer with unresectable liver metastases of colorectal cancer and have not received any anti-tumor treatment. Eligible patients will be assigned to effective group (group A) and drug resistance group (group B) according to the evaluation results of multidisciplinary team after 4-8 cycles of conversion therapy about 2-4 months.

Then, 5-hmC in plasma cell-free DNA will be detected and compared between the two groups of patients (training group) to establish a model to predict the efficacy of convertion therapy of other individuals (validation group) who suffer with unresectable liver metastases of colorectal cancer receiving conversion therapy.

Inclusion Criteria:

• Histologically proven colorectal adenocarcinoma
• Liver metastases were observed by abdominal pelvic CT and / or MRI with/without other distant metastases
• The liver metastases assessed as unresectable lesions by multidisciplinary team
• No other malignancies in medical history
• Eastern cooperative oncology group score 0-2
• Informed consent

Exclusion Criteria:

• Patients received chemoradiotherapy or other anti-tumor therapy before being enrolled
• Patients and/or family members can not understand or accept this study
• Familial Adenomatous Polyposis, Lynch Syndrome, acute inflammatory bowel disease
• Pregnancy or lactation
• Unsuitable to take part in the clinical trial judged by doctors

Patients with unresectable liver metastases from colorectal cancer were not received any anti-tumor therapy before being enrolled.