Impact of intramuscular fat accumulation on survival in stage II/III gastric cancer.

Abstract

19 Background: Intramuscular fat accumulation of skeletal muscle has been reported to be a prognostic factor in various cancers. To evaluate the intramuscular steatosis, intramuscular adipose tissue content (IMAC) measured by CT scan is thought to be an ideal method. However, this kind of study is very limited in curatively resected gastric cancer. So, this study was aimed to clarify the impact of IMAC on survival in stage II/III gastric cancer (GC). Methods: A total of 383 patients with pathological stage II/III GC after curative gastrectomy between January 2009 and December 2013 were included. IMAC was calculated by dividing the CT value of the multifidus muscles with that of the subcutaneous fat at the level of third lumbar vertebra. The IMAC cut-off values associated with cancer-specific survival (CSS) were separated by sex based on the maximum values of Youden index (sensitivity + specificity -1). Patients were classified into normal or high IMAC group according to this cut-off value. Clinicopathological factors and survival outcomes were compared between the two groups. Results: The median values of IMAC were -0.327 (IQR: -0.404- -0.250) in male and -0.239 (IQR: -0.335- -0.114) in female. The cut-off values of IMAC were -0.345 in male and -0.126 in female. Patients were classified into normal IMAC group (n = 204) and high IMAC group (n = 179). Patients in the high IMAC group were elderly, male, obese, having many comorbidities and with poor ECOG-PS compared to those in the normal IMAC group. Interestingly, despite the fact that no significant differences were observed in the pathological findings between the groups, the overall survival and CSS were significantly worse in the high IMAC group than in the normal IMAC group (p < 0.001 and p = 0.035). Moreover, the high IMAC was identified as an independent prognostic factor not only for overall survival but also for CSS (HR: 1.440, p = 0.021, HR: 1.646, p = 0.008, respectively). Conclusions: The high IMAC was significantly associated with worse survival, suggesting that IMAC represents certain oncological implications in patients with GC. Therefore, IMAC could be used as a new prognostic factor in curatively resected GC.