Laparoscopic colorectal surgery has been proved to have similar oncological outcomes with open surgery. Due to the lack of tactile perception, surgeons may have misjudgments in laparoscopic colorectal surgery. Therefore, the accurate localization of a tumor before surgery is important, especially in the early stages of cancer. Recently, some retrospective studies reported the use of patients' autologous blood for preoperative colonic localization in colorectal cancer with successful detection by laparoscopy, but its benefits remain controversial. This study aimed to assess the accuracy and safety of autogenous blood marker localization in laparoscopic radical resection for colorectal cancer.

Laparoscopic surgery has become the standard for management of colorectal cancer(CRC) with the advantages of less traumatic procedure, but similar oncological outcomes to open surgery. Due to the lack of tactile perception (haptic feedback), surgeons may have misjudgments in patients with small or flat early colon cancer, malignant polyps resected by endoscopic mucosal resection or endoscopic submucosal dissection. Therefore, the accurate localization of a tumor before surgery is important, especially in the early stages of cancer, to clarify the extent of surgical resection.

Several methods are currently being proposed and used to identify the location of tumors. These include endoscopic tattooing with India ink, indocyanine green (ICG), preoperative endoscopic metal clipping with detection using an x-ray or palpation during surgery, and intraoperative endoscopy.

Recently, some retrospective studies reported the use of patients' autologous blood for preoperative colonic localization in CRC with successful detection by laparoscopy. Autologous blood was thought a feasible and safe tattooing agent for preoperative endoscopic localization. Nonetheless, all currently available evidence comes from observational studies that are susceptible to bias. We therefore proposed to conduct this randomized controlled clinical trial to evaluate the accuracy and safety of autogenous blood marker localization in laparoscopic radical resection for colorectal cancer.

Inclusion Criteria:

1. Age from 18 to 80 years
2. Large lateral spreading tumors that could not be treated endoscopically, serosa-negative malignant colorectal tumors (≤ cT3), and malignant polyps treated endoscopically that required additional colorectal resection.
3. The tumor is located in the colon, middle and high rectum (the lower margin of the tumor does not exceed peritoneal reflexes)
4. No distant metastasis.
5. American Society of Anesthesiology score (ASA) class I-III
6. Performance status of 0 or 1 on Eastern Cooperative Oncology Group scale (ECOG)
7. Written informed consent

Exclusion Criteria:

1. BMI > 35kg/m2
2. Previous history of gastrointestinal surgery that altered the gastrointestinal anatomy.
3. Pregnant or lactating women
4. Severe mental disorder
5. History of previous abdominal surgery (except cholecystectomy and appendectomy) Rejection of laparoscopic resection
6. History of cerebrovascular accident within the past six months
7. History of unstable angina or myocardial infarction within the past six months
8. History of previous neoadjuvant chemotherapy or radiotherapy
9. Comorbidity of emergent conditions like obstruction, bleeding or perforation.
10. Needing simultaneous surgery for other diseases.