SOULMATE: the Swedish study of liver transplantation for isolated colorectal cancer liver metastases not suitable for operation or ablation, compared to best established treatment-a randomized controlled multicenter trial.

Background: Around one fourth of patients with colorectal cancer present themselves with distant metastases at the time of diagnosis, and one additional one fifth of the patients will develop distant metastases during the disease, most commonly in the liver. Surgical treatment such as liver resection or ablation, often combined with chemotherapy and targeted therapy, is the only treatment option with curative potential, but only about 20% of the patients with liver metastases are candidates for surgical intervention. Standard treatment for unresectable patients is palliative oncological therapy; however, less than 10% of these patients will achieve a 5-year survival. Non-randomized studies indicate that liver transplantation could be an option for selected patients with colorectal liver metastases (CRLM), which are not suitable for operation or ablation due to surgical technical reasons such as massive tumor burden and small future liver remnant, or oncological reasons, for example, early relapse after liver surgery. Since there is a shortage of donated liver grafts, it is important to select the patient group that benefit most from the treatment. Although some studies present positive results from liver transplantation of CRLM, the results must be validated in a randomized controlled trial before this new indication for liver transplantation can be introduced as a clinical routine.

Methods: The SOULMATE study is a randomized study evaluating if liver transplantation with liver grafts, primarily from extended criteria donors, increases overall survival in patients with CRLM, not suitable for resection or ablation, in comparison with best established treatment. Patients will be randomized to liver transplantation (LT)+ best established treatment (BET) or to best established treatment only. In the SOULMATE trial, we will evaluate the use of livers from extended criteria donors to decrease the risk of prolonging waiting time for patients on the waiting list for LT.

Discussion: The SOULMATE study has the possibility to confirm the positive results of previous studies in a randomized setting. The use of extended criteria donors will make the results transferable globally, as most countries are struggling with organ shortage.

Trial Registration: Clinical Trial number: NCT04161092 registered 13 November 2019.