Colorectal cancer (CRC) is a malignant disease of the colon or rectum and represents the third most frequently diagnosed cancer in both men and women. Over the course of their disease, approximately half of all CRC patients will develop colorectal liver metastases (CRLM). (Bray et al., 2024)
Currently, liver resection remains the only potentially curative option for patients with CRLM. However, only 10% to 30% of patients present with disease that is considered resectable. In the United States alone, more than 76,000 new cases of CRLM were projected for 2023, yet only an estimated 23,000 of these patients were expected to have resectable disease. The survival benefits of surgery are significant: the 5-year relative survival rate after partial liver resection is between 20% and 45%, compared with only 6% for patients with unresectable CRLM. (Cucchetti et al., 2015)
Resectability criteria are strict: complete removal of the CRLM must be possible, at least two adjacent liver segments must remain, and sufficient vascular inflow/outflow and biliary drainage must be preserved. Additionally, the future liver remnant (FLR) must comprise at least 20% of the total estimated liver volume. Tumors are deemed unresectable when more than 70% of the liver or more than six segments are involved, or when there is invasion of the portal vein or all hepatic veins. Importantly, the risk of post-hepatectomy liver failure (PHLF) rises steeply with the extent of resection, approaching nearly 100% when more than 70% of the liver is removed. While mild PHLF (grade A) carries no mortality, severe PHLF (grade C) is associated with a mortality rate as high as 54%. (Rahbari et al., 2011)
Therefore, operability is determined largely by the adequacy of the remaining liver volume. The balance between the extent of tumor removal and preservation of sufficient functional liver tissue is critical for survival outcomes and has direct implications for strategies aiming to expand resectability and improve postoperative safety. Operability, therefore, largely depends on the extent of the remaining future liver.