Borderline resectable for colorectal liver metastases: Present status and future perspective

Surgical resection for colorectal liver metastases (CRLM) may offer the best opportunity to improve prognosis. However, only about 20% of CRLM cases are indicated for resection at the time of diagnosis (initially resectable), and the remaining cases are treated as unresectable (initially unresectable). Thanks to recent remarkable developments in chemotherapy, interventional radiology, and surgical techniques, the resectability of CRLM is expanding. However, some metastases are technically resectable but oncologically questionable for upfront surgery. In pancreatic cancer, such cases are categorized as "borderline resectable", and their definition and treatment strategies are explicit. However, in CRLM, although various poor prognosis factors have been identified in previous reports, no clear definition or treatment strategy for borderline resectable has yet been established. Since the efficacy of hepatectomy for CRLM was reported in the 1970s, multidisciplinary treatment for unresectable cases has improved resectability and prognosis, and clarifying the definition and treatment strategy of borderline resectable CRLM should yield further improvement in prognosis. This review outlines the present status and the future perspective for borderline resectable CRLM, based on previous studies.