Colorectal cancer is currently the third most common malignant tumor in the world, and about 20%-50% of patients have liver metastases at the time of diagnosis or progress to liver metastases thereafter. The liver is the most frequently invaded organ by colorectal cancer, and liver resection is considered to be the best and only treatment option for patients with colorectal liver metastases (CLMs). However, only about 20% of patients are candidates for radical hepatectomy. For most patients who are not candidates for hepatectomy, palliative chemotherapy is the only option. Regrettably, the median survival time of all patients receiving chemotherapy is only 2 years, and the 5-year survival rate is only 10%.

Theoretically, liver transplantation is an ideal choice for patients with unresectable colorectal liver metastases (Irresectable Colorectal Liver Metastases, iCRLM). In a clinical study in Norway, 21 patients with iCRLM were enrolled and treated with liver transplantation, although 19 patients had recurrence and metastasis after transplantation (median time 6 months, range 2-24 months). However, the 1-year, 3-year and 5-year survival rates rose to 95%, 68% and 60% after surgery. In this study, the risk factors for poor prognosis after liver transplantation in iCRLM patients were summarized: the largest tumor diameter was more than 5.5 cm, CEA before transplantation was \>80ug/ml, the interval between primary disease surgery and transplantation was less than 2 years, and poor response to chemotherapy. Subsequently, the center conducted a second study and performed liver transplantation on 15 patients with iCRLM after optimizing the inclusion criteria. The 1-year, 3-year, and 5-year survival rates were 100%, 83%, and 83%, and the recurrence-free survival rates were 53%, 44%, and 35%. The above studies have proved that liver transplantation can significantly improve the prognosis of patients with iCRLM. However, the shortage of donor livers is the most serious problem faced by iCRLM patients. Moreover, iCRLM is generally considered a contraindication for liver transplantation, so it is more difficult for patients with iCRLM to obtain a donor liver.

Therefore, expanding the donor liver pool is urgently needed for the treatment of patients with iCRLM. In 2015, Norwegian scholars proposed a new surgical method, that is, resection and partial liver segment 2-3 transplantation with delayed total hepatectomy (RAPID) . This approach allows transplantation of the left liver (segments 2+3) to an adult recipient, while the remaining enlarged right hemi-liver is transplanted to another adult recipient, effectively avoiding some unsuitable left lateral lobe livers for pediatric recipients to be wasted. Recipients who received right-hemi-liver transplantation had a similar prognosis compared with those who received whole-liver transplantation. Therefore, if the RAPID technique is confirmed to be feasible, it can greatly alleviate the shortage of liver donors. In addition to cadaver sources, living adult donors can also be considered as the source of liver donors. A smaller left lateral lobe donor liver also places less burden on the donor than a left or right hemiliver.

To sum up, our center proposed and designed a clinical study of sequential adult left lateral lobe liver transplantation (SALT) in the treatment of patients with iCRLM based on clinical surgical experience. On the basis of RAPID surgery, the overall survival rate of patients with iCRLM was evaluated by SALT.