A Systematic Review of Disappearing Colorectal Liver Metastases: Resection or No Resection?

Background: Colorectal cancer is the second most common type of cancer and a leading cause of cancer-related deaths worldwide. Approximately 15% of the patients with colorectal cancer will already have liver metastases (CRLMs) at diagnosis. Luckily, the advances in chemotherapy regimens during the past few decades have led to increased rates of disease regression that could even render an originally unresectable disease resectable. In certain patients with CRLMs, the hepatic lesions are missing on preoperative imaging after neoadjuvant chemotherapy. These patients can undergo surgery with or without resection of the sites of the disappearing liver metastases (DLMs). In this systematic review, we assess the recurrence rate of the DLMs that were left unresected as well as the complete pathologic response of those resected. Methods: A literature search was conducted in PubMed for studies including patients with CRLMs who received neoadjuvant chemotherapy and had DLMs in preoperative imaging. Two independent reviewers completed the search according to the PRISMA checklist. Results: Three hundred and twenty-six patients with 1134 DLMs were included in our review. A total of 47 out of 480 DLMs (72.29%) that were removed had viable tumor cells in postoperative histology. One hundred and forty-five tumors could not be identified intraoperatively and were removed based on previous imaging, with thirty (20.69%) of them presenting viable cancer cells. Four hundred and sixty-five lesions could not be identified and were left in place. Of them, 152 (32.69%) developed local recurrence within 5 years. Of note, 34 DLMs could not be categorized as viable or non-viable tumors. Finally, DLMs that were identifiable intraoperatively had a higher possibility of viable tumors compared to non-identifiable ones (72.29% vs. 20.69%, respectively). Conclusions: Disappearing liver metastases that are left unresected have an increased possibility of recurrence. Patients receiving neoadjuvant treatment for CRLMs may have better survival chances after resecting all the DLM sites, either identifiable intraoperatively or not.