Precision Surgery of Colorectal Liver Metastases in the Current Era: A Systematic Review

SIMPLE SUMMARY: Colorectal cancer is among the most commonly encountered human malignancies, with up to a quarter of total patients exhibiting metastatic spread to the liver at some point during the disease course. For these patients, curative-intent liver resection yields the optimal oncological outcomes, ensuring long-term survival in the majority of cases. However, taking into account that liver resections are accompanied by considerable postoperative complication rates, treatment approaches should be individualized to avoid unnecessary exposure to morbid therapies. To that end, the study of tumor biology, especially in terms of RAS mutational status, is proving a very helpful adjunct in identifying patient subsets that derive the most benefit from this aggressive treatment modality. The concept of precision surgery in CRLM revolves around tailoring the aggressiveness of the employed treatments depending on tumor features, while avoiding surgery in patients not expected to derive any benefit from it. ABSTRACT: Liver resection for colorectal liver metastases (CRLM) is widely considered the treatment with the highest curative potential. However, not all patients derive the same oncological benefit, underlining the need for better patient stratification and treatment allocation. In this context, we performed a systematic review of the literature to determine the role of RAS status in selecting the optimal surgical strategy. Evidence comparing anatomical with non-anatomical resections depending on RAS mutational status was scarce and conflicting, with two studies reporting superiority in mutated RAS (mutRAS) patients and two studies reporting equivalent outcomes. The rate of incomplete microscopic resection (R1) was found to be increased among mutRAS patients, possibly due to higher micrometastatic spread lateral to the primary lesion. The impact of R1 resection margins was evaluated separately for mutRAS and wild-type patients in three studies, of which, two indicated an additive detriment to long-term survival in the former group. In the current era of precision surgery, RAS status can be utilized to predict the efficacy of liver resection in the treatment of CRLM, avoiding a potentially morbid operation in patients with adverse tumor profiles.