New definition of borderline resectable colorectal liver metastasis based on prognostic outcomes.

Background: Although surgical resection is the curative treatment for colorectal liver metastases (CRLM), the efficacy of neoadjuvant chemotherapy (NAC) has been discussed due to recent remarkable advances in chemotherapy. The definition of borderline resectable (BR) is most important, where neoadjuvant chemotherapy should be administered. This study aimed to examine a new definition of BR CRLM based on the results of the treatment outcomes.

Methods: This study included 127 patients who underwent liver resection for CRLM after exclusion of conversion cases between April 2010 and December 2023. Upfront resection was performed for synchronous and single liver metastasis or metachronous liver metastases. NAC was administered for multiple synchronous liver metastases. In order to find a new definition of BR, we examined the prognostic factors obtained from the treatment outcomes.

Results: CA19-9 level > 37.0 was the only prognostic factor in the upfront group [hazard ratio (HR) 2.386, 95% CI, 1.583-4.769; p = 0.049]. in the NAC group, a maximum tumor diameter ˃3 cm (HR 2.248, 95% CI 1.038-4,867, p = 0.040), CA19-9 level > 37.0 (HR 2.239, 95% CI 1.044-4.800, p = 0.038), and a right-sided primary tumor in the colon (HR 2.770, 95% CI 1.284-5.988, p = 0.009) were identified as significant prognostic factors.

Conclusions: In cases of CRLM, patients with CA19-9 levels > 37.0, or CA19-9 level with < 37.0 but with a primary tumor in the right colon or a maximum tumor diameter of > 3 cm can be defined as BR CRLM and should be treated with NAC.