Prognostic value of sarcopenia in patients with colorectal liver metastases undergoing hepatic resection

The prognostic significance of sarcopenia has been widely studied in different cancer patients. This study aimed to analyze the influence of sarcopenia on long-term survival in patients with colorectal liver metastasis (CRLM) undergoing hepatic resection. A retrospective analysis of 182 patients undergoing hepatic resection for CRLM was performed. Sarcopenia was determinedusing the Hounsfield unit average calculation (HUAC), a measure of muscle quality-muscledensity at preoperative abdominal computed tomography scans. Sarcopenia was defined as an HUAC score of less than 22 HU calculated using receiver operating characteristic analysis. The prognostic relevance of clinical variables and overall survival (OS) and recurrence-free survival (RFS) was evaluated. Patients with sarcopenia were older (p < 0.001) and had higher prevalence of diabetics (p = 0.004), higher body mass index (BMI) (p < 0.001) and neutrophil-to-lymphocyte ratio (p = 0.026) compared to those without. Sarcopenia was not significantly associated with OS and RFS. Multivariate Cox’s regression analysis showed that multinodularity (>3) (hazard ratio (HR) 2.736; 95% confidence interval (CI), 1.631–4.589; p < 0.001), high CEA level (≥20 ng/ml) (HR 1.793; 95% CI, 1.092–2.945; p = 0.021) and blood loss (≥300 cc) (HR1.793; 95% CI, 1.084–2.964; p = 0.023) were independent factors associated with OS. In subgroup analyses, sarcopenia was a significant factor of poor OS in the patients with multinodularity by univariate (p = 0.002) and multivariate analyses(HR 3.571; 95% CI, 1.508–8.403; p = 0.004). Multinodularity (>3) (HR 1.750; 95% CI, 1.066–2.872; p = 0.027), high aspartate aminotransferase level (HR 1.024; 95% CI, 1.003–1.046; p = 0.025) and male gender (HR 1.688; 95% CI, 1.036–2.748; p = 0.035) were independent factors of RFS. In conclusion, despite no significance in whole cohort, sarcopenia was predictive of worse OS in patients with multiple CRLM after partial hepatectomy.

. Baseline characteristics of the study cohort. * C/A/T/D/S/RS/R: cecum/ascending colon/transverse colon/descending colon/sigmoid colon/recto-sigmoid colon/rectum.Abbreviation: DM, diabetes mellitus; CEA, carcinoembryonic antigen; aspartate aminotransferase; ALT, alanine aminotransferase; NLR, neutrophil-tolymphocyte ratio. Image analysis. Preoperative abdominal CT scans were performed on a GE Discovery CT750 HD lightspeed scanner. Evaluation for sarcopenia was performed using CT measures ofmuscle quality-muscledensity (measured in Hounsfield units (HU))as previously described [19][20][21] . All measurements and segmentations were done at the level of the inferior endplate of L4 on axial CT images. To measure muscle density, the paraspinal muscles were outlined using a freehand region-of-interest (ROI) tool on a General Electric Picture Archiving and Communicating System (S1000). The total cross-sectional area of bilateral paraspinal, psoas, and abdominal wall muscles at L4 were evaluated on OsiriX imaging software v. 8.0.2 (Pixmeo, Geneva, Switzerland) with the lean muscle threshold set at −29 to 150 HU [19][20][21] . The final Hounsfield unit average calculation (HUAC)was the average ofleft HU and right HU to determine the presence or absence of sarcopenia in the study population.
Follow-up. The regimens of chemotherapy included fluorouracil and leucovorin, combined with irinotecan and/or oxaliplantin, which was currently the standard treatment for CRLM. Follow-up consisted of out patient visits with serum carcinoembryonic antigen (CEA) levels and imagesevery 3 to 6 months after surgery. Overall survival (OS) was defined as the time interval from the date of hepatic resectionto death from any cause or the last follow-up date. Recurrence-free survival (RFS) was defined as the period after hepatic resection to the date when recurrent tumors were diagnosed.
Statistical analysis. Continuous data were presented as mean ± standard deviation and compared by using Student's t test. Categorical variables were expressed as number (percentage) and analyzed by using the χ 2 or Fisher's exact test depending on the size of the sample. A receiver-operating characteristic (ROC) curve was used to determine the best cutoff of HUAC scorebased on the Youden index. Kaplan-Meier curves were generated for OS and RFS and the differences of survival rates between groups were compared using the log-rank test. The Cox proportional hazards model was employed for univariate and multivariate analyses. The analysis software used was SPSS for Windows version 18 (SPSS Inc., Chicago, IL, USA). All statistical tests were two-sided and differences were considered significant with a p < 0.05.

Results
Patient characteristics. Among the study population, the mean age was 59.5 ± 12.1 years with a range 21-85 years, and 106 of them were male. Sixty-twopatients had solitary tumor whereas 57 had 2-3 tumors, and 63 had more than 3 tumors. Neoadjuvant chemotherapy was given in 35 of 182 patients (19.2%), and 166(91.2%) patients received adjuvant chemotherapy after hepatic resection (Table 1).
ROC analysis for HUAC score in the survival status at the 5-year follow-up identified an optimal cutoffat HUAC of 22 HU. At this cutoff, 48 (26.4%) patients were considered sarcopenic. Patients with sarcopenia were older (p < 0.001) and had higher prevalence of diabetics (p = 0.004), higher body mass index (BMI) (p < 0.001)
In subgroup analyses, sarcopenia was a significant factor of poor OS in the patients with multinodularity (p = 0.001) (Fig. 2). In contrast, there were no associations of sarcopenia with OS in other subgroup analyses, such as age, gender, diabetes, tumor size, etc. Table 4 shows thefactors associated with OS in subgroup patients with multiple CRLM. Sarcopenia was the significant factor associated with poor OS in the patients with multiple CRLM by univariate (p = 0.002) and multivariate analyses(HR 3.571; 95% CI, 1.508-8.403; p = 0.004).

Discussion
This present study showed that preoperative sarcopenia was not associated with long-term survival in a homogeneous population of CRLM undergoing hepatic resection. Sarcopeniawas not a significant risk factor of OS and RFS in our study population. However, our study provided the first evidence that sarcopenia predicted worse OS in the subgroup patients with multinodularity (>3).
A number of clinicopathological factors have been constantly reported as having prognostic value following hepatectomy of CRLM 8,9,[22][23][24] . In this study, we demonstrated that multinodularity (>3), high CEA level (≥20 ng/ ml) and blood loss (>300 cc) were independent factors associated with poorer OS. Our data were compatible with those reported in most studies 8,9,[22][23][24] , showing that the number of liver metastaseswas the most important negative predictor not only for OS but also for RFS. In contrast, the location of primary tumoremerging as an  www.nature.com/scientificreports www.nature.com/scientificreports/ important prognostic factor was not significant in our study 25 . This could be attributed to the small case number of right sided cancer in this series.
Recently, the use of sarcopenia to predict outcomes in cancer patients has attracted more attention, including those with CRLM undergoing hepatic resection. Previous studies demonstrated that sarcopenia increased risk of post-operative morbidity and longer hospital stay as well as readmission ratesafter partial liver resection for CRLM 15,18 . On the contrary, sarcopeniadid not seemto impact long-term outcomes in their patients. Our data, in line with their results, showed that sarcopenia was not a significant risk factor of OS and RFS. Moreover, considering the greater impact of other stronger risk factors such as tumor number, we therefore analyzed the effect of www.nature.com/scientificreports www.nature.com/scientificreports/ sarcopenia on the subgroups of our patients. Interestingly, we found that sarcopenia was significantly predictive of worse OS in the patients with multiple CRLM. Based on our findings, we recommended that patients with multiple (>3) CRLM and combined sarcopenia, hepatic resection might be considered cautiously due to limited survival. However, further studies with longer follow-up periods should be necessary to confirm our observation.
In our study population, sarcopenia was associated with advanced age, diabeticsand obesity. Although these results were discrepant with other findings 15,26 , our data were consistent with a recent report showing that age and obesity were found to be independently associated with sarcopenia in patients undergoing liver transplant evaluation 27 . Previous studies have reported that patients with sarcopenic obesity had worse survival in hepatocellular carcinoma receiving hepatectomy or after living donor liver transplantation [28][29][30][31] . While our data in accordance with a recent study showed that sarcopenicobesity was not a prognostic factor in patientsundergoingliver resection for CRLM 32 .
This present study is limited based on its retrospective nature and thus there may have been selection bias. Moreover, we believed that the bias was smallbecause patientswere followed regularly with clinical and laboratory assessment using CEA and imaging studies every 3 to 6 months. Secondly, we defined obesity as BMI≧25 kg/ m 2 by clinical diagnosis, whereas other studies assessed the visceral adipose tissueusing CT evaluation 18,29 . However, a previous study has showna close positive correlation of BMI with visceral adipose tissue, andobesity is adequately specified as a BMI≧25 kg/m 2 in Asian populations 33 . Third, the recent novel mutational molecular markers, such as microsatellite instability, BRAF, and KRAS/NRAS and combination mutations which conferred poorer outcomeswere not available in our study 24 . It willbe interesting to determine the association of molecular markerswith long-term prognosisin patients with CRLM after partial hepatectomy in further studies.
In conclusion, in spite of no significance in long-term outcomes in whole cohort, sarcopenia is associated with an increased survival risk of patients with multiple CRLM undergoing hepatic resection. Assessment of preoperative sarcopenia provides an easy tool for selection of CRLM patients for liver resection. Further large-scale and multicenter studies are stillneeded to clarify these issues.