Skeletal muscle index (SMI) status and survival in patients undergoing surgery for colorectal cancer (CRC): A longitudinal study.

Abstract

175 Background: There is now good evidence that low skeletal muscle index (SMI) using established thresholds is associated with poor survival in patients undergoing surgery for CRC. However, to date few studies have carried out longitudinal analyses. Such studies also inform, the determinants of SMI status. Methods: From prospectively maintained database, pre-operative and 1 year follow up CT scans were analysed at L3 level for SMI (n=794).The relationship between SMI status before and after surgery (both high (n=366)/high then low (n=52)/low then high (n=108) and both low (n=268), clinicopathological parameters and overall survival was analysed. Results: The majority of patients were > 65 years of age (75%), male (56%), ASA<3 (67%), had TNM stage <3 (65%) and were not systemically inflamed (mGPS = 0 in 73%, and NLR <3 in 53%). Patients with low SMI at any time point (before surgery, after surgery, or both) had significantly poorer survival (p<0.001), were more likely to be over 65 years (p<0.001), and with mGPS>0 (p<0.001) than those who had high SMI at both time points. In those patients who were high then low SMI, they had poor survival (p<0.001) and were more likely >65 years old (p<0.001) compared with high high SMI. There was no difference in survival between those with low high SMI compared with low low SMI status (p=0.296). Conclusions: In this longitudinal study, low SMI status was associated with older age, increased systemic inflammatory response and poorer survival whether prior to or following surgery for CRC. Interestingly, surgery did not affect preoperative SMI status in the majority of patients, suggesting that host responses perhaps have a greater effect than the presence of the tumour itself. Reference: Martin L, Birdsell L, Macdonald N, et al. Cancer cachexia in the age of obesity: skeletal muscle depletion is a powerful prognostic factor, independent of body mass index. J Clin Oncol. 2013;31: 1539-1547.