In this study, the investigators establish a model for the early diagnosis of colorectal cancer based on detection of 5-hydroxymethylcytosine (5-hmC) in training group and validate the effectiveness of the model using a validation group.

Many kinds of cancers are associated with changes in epigenetics, including 5-methylcytosine (5-mC) and 5-hydroxymethylcytosine (5-hmC). This changes may help diagnose cancer. The new detection method for 5-hmC can meet the requirements of liquid biopsy.

The traditional diagnostic methods for colorectal cancer is colonoscopy and pathology which are inconvenient and unpleasant, and sometimes, it is difficult for the very patients to get tissues or get enough tissues. In addition, other screening methods for colorectal cancer,such as guaiac-based fecal occult blood testing and a blood test for methylated SEPT9 DNA, have the shortcomings of relatively low sensitivity and specificity. As a result, it is imperative to find a new detection method for early diagnosis of colorectal cancer with high the advantages of high sensitivity and specificity, minimally invasive and convenient.

The aim of this research study is to establish a model for the early diagnosis of colorectal cancer by the detection of 5-hmC in plasma cell-free DNA. Patients who are diagnosed with colorectal cancer by colonoscopy and pathology and not received any anti-tumor therapy (Arm A) will be eligible for inclusion as well as healthy individuals with normal colonoscopy (Arm B). Then, 5-hmC in plasma cell-free DNA will be detected and compared between the two arms of patients (training group) to establish a model to diagnosis other people (validation group) who may suffer from colorectal cancer.

Inclusion Criteria:

Arm A

• Histologically proven colorectal adenocarcinoma
• No other malignancies in medical history except adequately treated basocellular carcinoma of the skin or in situ carcinoma of the cervix uteri
• Eastern cooperative oncology group score 0-2
• Informed consent

Arm B

• Healthy people with normal colonoscopy
• No other malignancies in medical history except adequately treated basocellular carcinoma of the skin or in situ carcinoma of the cervix uteri
• Eastern cooperative oncology group score 0-2
• Informed consent

Exclusion Criteria:

Arm A

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

Arm B

• Pregnancy or lactation
• Unsuitable to take part in the clinical trial judged by doctors

Adults diagnosed with colorectal cancer or with normal colonoscopy.