Resection of liver metastases from colorectal mucinous adenocarcinoma: is this a different disease? Results of a case-control study.

OBJECTIVES: To compare outcomes following liver resection of colorectal metastases (CRLM) from mucinous adenocarcinoma (Muc-CRLM) versus nonmucinous adenocarcinoma (non-Muc-CRLM). BACKGROUND: Among colorectal adenocarcinomas, 10%-15% are mucinous and have worse prognoses than nonmucinous ones. Outcomes of liver resection for Muc-CRLM remain unknown. METHODS: Among 701 patients undergoing liver resection for CRLM between 1998 and 2012, 102 (14.6%) had Muc-CRLM. Each was matched with a non-Muc-CRLM patient, based on tumor N status, disease-free interval (DFI) between primary tumor and metastases, CRLM number and diameter, extrahepatic disease, and preoperative chemotherapy. RESULTS: Within the 2 groups, 69.6% of patients had N+ primary tumor, 72.5% had DFI of less than 12 months, 28.4% had 4 or more CRLM, and 22.5% had associated extrahepatic disease. 59.8% of patients received preoperative chemotherapy. Muc-CRLM patients had higher prevalences of right/transverse colon cancer (55.9% vs 29.4%; P<0.0001) and K-ras mutation (67 patients tested, 61.8% vs 36.4%; P=0.037), as well as lower response to preoperative chemotherapy (63.9% vs 85.2%; P=0.006). Multivariate analysis showed Muc-CRLM to have lower rates of 5-year overall (33.2% vs 55.2%; P=0.010) and disease-free survival (32.5% vs 49.3%; P=0.037). Muc-CRLM recurrence was more often peritoneal (20.3% vs 6.5%; P=0.024) and at multiple sites (47.5% vs 21.0%; P=0.002), and had lower rates of re-resection (16.9% vs 43.5%; P=0.002) and 3-year post-recurrence survival (11.7% vs 43.4%; P=0.0003). CONCLUSIONS: Muc-CRLM patients strongly differed from non-Muc-CRLM patients, showing a lower chemotherapy response and higher K-ras mutation prevalence. Muc-CRLM appears to be a separate disease, which is associated with worse survival and aggressive rarely re-resectable recurrences.