After the surgery of colorectal cancer, the doctor said the surgery was successful and asked for regular review, but this review found liver metastasis…… Why is colorectal cancer easily metastasized to the liver? The organ where colorectal cancer is most likely to metastasize is the liver. Why is it that colorectal cancer is most likely to metastasize to the liver? Because physiologically, the venous blood of human intestine has to transport various nutrients such as sugar, protein and fat absorbed by the intestine into the liver through the portal vein, where they are absorbed and reprocessed to supply the body with what it needs. In other words, the blood from the intestine mainly returns to the liver, therefore, the liver is the main target organ for blood-borne metastasis of intestinal cancer. In the whole course of colorectal cancer patients, more than 50% of them will develop liver metastasis before or after colorectal cancer surgery. Can colorectal cancer liver metastasis be operated? In the past, it was believed that once metastasis occurred, the patient had reached an advanced stage and lost the chance of surgical treatment. Nowadays, based on the establishment of multidisciplinary integrated treatment platform and the deepening of multidisciplinary collaboration (MDT) concept, the treatment strategy for liver metastasis of colorectal cancer has been revolutionized. Surgical resection is the only possible cure for liver metastasis of colorectal cancer. Clinically, about 20% of patients with liver metastases from intestinal cancer are able to undergo surgical resection of liver metastases. These patients are characterized by liver metastases only, small size and number of lesions, concentration of metastases in one or two liver lobes, and the ability to preserve sufficient liver volume after resection of metastases. Patients who undergo surgical resection combined with postoperative adjuvant chemotherapy have a better prognosis, with a five-year survival rate of about 50%. What about liver metastases that cannot be surgically resected? Even if surgical resection is not possible, there are many treatment methods for liver metastases from colon cancer. Among them, systemic treatment includes chemotherapy, targeted therapy and immunotherapy, while local treatment includes local ablation therapy, interventional therapy, radiotherapy and so on. It is certain that active and effective comprehensive treatment can control the rapid progression of the disease and significantly prolong the survival time of patients. I. Systemic chemotherapy combined with targeted therapy Since the emergence of two cornerstone chemotherapy drugs, irinotecan and oxaliplatin in the 1990s, the treatment of unresectable advanced colorectal cancer has fully entered the era of chemotherapy. Currently, the commonly used chemotherapeutic agents for colorectal cancer include 5-FU/LV, irinotecan, oxaliplatin, capecitabine, trifluridine tipiracil and raltitrexed. Commonly used targeted drugs include cetuximab, bevacizumab, regorafenib and furoquinitinib. How do you choose from the many drugs available? In fact, before developing a treatment plan, patients need to undergo genetic testing, including RAS and BRAF, as well as testing for PIK3CA and microsatellite instability (MSI) genes, and decide on a chemotherapy/targeted therapy regimen based on genotyping. Clinical evidence suggests that two-drug chemotherapy combined with anti-EGFR monoclonal antibody is a better treatment option for patients with RAS/BRAF wild-type left hemizygous colon cancer. For patients with RAS/BRAF wild-type right hemico-rectal cancer, two-drug combination with anti-VEGF monoclonal antibody is an option. For patients with RAS gene mutation, chemotherapy combined with anti-VEGF monoclonal antibody can be an option. Immunotherapy In recent years, immunotherapy has been a hot spot in major cancer research. In the field of colorectal cancer, studies targeting the MSI-H/dMMR population have been carried out since 2015. Several clinical studies have shown that immunotherapy is the first choice for MSI-H patients, and chemotherapy combined with targeted therapy is the second choice, because immunotherapy can better delay tumor progression and prolong survival time compared with chemotherapy/targeted therapy alone. Moreover, compared with chemotherapy, the overall toxic side effects of immunotherapy are significantly lower than those of chemotherapy/targeted therapy and well tolerated by patients. However, MSI-H bowel cancer patients only account for about 5% of the overall population, and the remaining 95% are MSS-type bowel cancer patients. For this group of patients, the 2019 REGONIVO study found that combining PD-1 monoclonal antibody with regorafenib, the third-line standard of care for bowel cancer, achieved a 36% efficiency rate. The MEDETREME trial study published this year at the American Society of Clinical Oncology Annual Meeting (ASCO) found that FOLFOX6 chemotherapy combined with durvalumab (D drug) and tremelimumab (T drug) treatment achieved a tumor remission rate of 62.5% and a tumor disappearance (CR) rate of 25%, showing good therapeutic efficacy. III. Local treatment 1. radiofrequency microwave ablation (RFA) and ablation (MWA) treatment For patients with a small number of liver metastases and small size, and patients whose general condition is not suitable or unwilling to receive surgical treatment, radiofrequency ablation or microwave ablation is recommended. Radiofrequency ablation for liver metastases requires a maximum tumor diameter of <3 cm and a maximum of <5 ablations at a time. Microwave ablation MWA is suitable for single tumor within 5cm in diameter, or small and medium-sized tumors with maximum diameter ≤3cm and number ≤3. 2.Interventional treatment For patients with colorectal cancer liver metastases with large number of tumors and large tumor load, especially those with poor efficacy of chemotherapy and targeted therapy, interventional treatment can be adopted to improve the efficacy of local treatment in liver. Interventional treatment methods for liver metastases from colorectal cancer include four types: hepatic artery chemoembolization (TACE), drug-laden microsphere intervention (DEB-TACE), hepatic artery chemoinfusion (HAIC) and hepatic artery radioembolization (TARE). The specific choice of interventional modality depends on the patient's tumor size, number, blood supply, previous treatment history and physical tolerance. 3.Radiotherapy The radiotherapy of metastases of intestinal cancer generally needs to be discussed by doctors from multiple disciplines to finally develop the most reasonable treatment plan. -It is generally judged according to the following aspects: (1) the size, number and specific location of metastases; (2) the patient's acceptance of other treatments; (3) the functional status of metastatic organs, such as liver, itself; and (4) the control of tumors in other parts. The main purpose of radiation therapy for colorectal cancer metastases is to reduce the local symptoms of the tumor and play a radical role in the small number or isolated lesions. In the past 5-10 years, colon cancer has seen rapid development in chemotherapy, targeted therapy, immunotherapy and local treatment, and new therapeutic drugs and treatments have emerged continuously, which greatly prolong the survival of patients. Patients with liver metastases from colon cancer need to implement individualized and comprehensive treatment plans based on multidisciplinary discussions to better prolong survival.