The sarcopenia index measured using the lumbar paraspinal muscle is associated with prognosis in endometrial cancer

Objective: The number of type-II endometrial cancer patients has been increasing and the prognosis is not favorable. We aim to investigate whether sarcopenia index in any of several different muscles could serve as a novel biomarker of prognosis in patients with type-II endometrial cancer. Methods: We retrospectively investigated a total of 194 patients at four hospitals. Ninety patients were treated as derivation set and the other 104 patients as validation set. Using preoperative computed tomography images, we measured the horizontal cross-sectional area at the third lumbar spine level: the (i) psoas major, (ii) iliac and (iii) paraspinal muscle. The clinical information including recurrence-free survival and overall survival were retrospectively collected. These results were validated with external data sets of three hospitals. Results: The median values of the sarcopenia index (cm2/m2) ± standard deviation with the first data of 90 patients using the psoas, iliac and paraspinal muscle were 3.4 ± 1.0, 1.7 ± 0.6 and 12.6 ± 3.2, respectively. In univariate analyses, the sarcopenia indexes measured using the psoas or paraspinal muscle were associated with recurrence-free survival and overall survival. On the other hand, in multivariate analyses, only the sarcopenia index using paraspinal muscle was significantly related to recurrence-free survival (hazard ratio = 3.78, 95% confidence intervals = 1.29-5.97, P = 0.009) and overall survival (hazard ratio = 3.13, 95% confidence interval = 1.18-8.26, P = 0.022). Paraspinal sarcopenia index was also related to overall survival (hazard ratio = 3.74, 95% confidence interval = 1.31-10.72, P = 0.014) even in patients with advanced stage. Serum albumin was significantly correlated with the sarcopenia index (P = 0.012). Within the analysis of the validation set, sarcopenia index using paraspinal muscle was related to recurrence-free survival (hazard ratio = 2.06, P = 0.045) in multivariate analysis and recurrence-free survival (P = 0.009) in patients with advanced stage. Conclusions: The sarcopenia index using the paraspinal muscle, not psoas, could be a suitable index to predict recurrence-free survival and overall survival in patients with type-II endometrial cancer even in advanced stage.