The body immunity is important to the development of tumor. The immune system is in charge of monitoring and cleaning tumor cells in circulation. Anesthesia may alter the immune response and affect the elimination of tumor cells. The purpose of the trial is to test whether inhalational anesthetic is relevant to tumor metastasis and recurrence of patients undergoing colorectal cancer resection through depression of lymphocytes-mediated immunity.

With the increasing number of patients diagnosed with colorectal cancer, the proportion of patients undergoing surgical resection with general anesthesia increased. However, the operation can lead tumor cells releasing into the blood or peritoneal implantation, and the impaired immune response can make patients susceptible to the development of tumor metastasis and recurrence which is the the main reason of death. It is well known that B lymphocytes and T lymphocytes are the main immune cells, and B lymphocytes by secreting antibodies are related to humoral immunity and T lymphocytes which play the most important role in antitumor are related to cell-mediated immunity. Surgery stress leads to metabolic and neuroendocrine changes causing significant depression of immunity. Although general anesthesia could reduce surgical stress, studies indicated general anesthetics including intravenous and inhalational agents both have variable effects on tumor cells growth by immuno-modulation and some cytokines. A number of studies have demonstrated deleterious effects on the function of lymphocytes associated with the administration of volatile inhalational anesthetic agents. It was suggested that the use of volatile inhalational agent may augment tumor cells growth by inhibiting the activity of lymphocytes, NK cells and dendritic cells which are important for recognizing, capturing and killing tumor cells, however, the alternative propofol has a converse (beneficial) effect by decreasing the plasma level of cytokines secreted by activated lymphocytes, macrophages and NK cells. The detailed mechanism of how volatile anesthetics affect the activity of antitumor cells remains unknown. Thus the investigators will conduct the clinical investigation to study the effect of volatile anesthetics on the immune response and metastasis in patients undergoing colorectal cancer resection, exploring molecular mechanism involved if inhalational anesthetics show an effect. The findings of this study would be valuable for anesthetic regimen guidance of colorectal cancer patients undergoing surgical resection in terms of long-term survival.

Inclusion Criteria:

• All the patients diagnosed with colonal or rectal cancer
• Aged 18-65
• ASA I-III
• Assigned to receive resection surgery under general anesthesia, with an expected duration of 2 hours or more
• Agree to participate and give signed written informed consent.

Exclusion Criteria:

• Severe organic heart, liver and kidney diseases
• Diabetes or hemopoietic disorders
• Allergy to general anesthetics
• Family historical malignant hyperthermia
• Cognition dysfunction
• End-stage cancer or with over 2 cancer metastasis, pathological results were benign tumor or TNM stage was over T1- 3N0 - 2M0
• Other primary malignant tumor
• Immune deficiency or dysfunction or autoimmune disease or long-term usage of corticoids or immunosuppressants
• Receiving general anesthesia within the last 3 months before the resection surgery
• Perioperative transfusion

Patients with colonal or rectal cancer undergoing cancer resection with general anesthesia

All the study outcomes