Higher Skeletal Muscle Index Is Associated with Improved Overall Survival in Older Patients with Sarcopenia Undergoing Allogeneic Stem Cell Transplant

Introduction: Allogeneic stem cell transplantation (allo-SCT) can be curative for patients with hematologic malignancies. Despite optimization of supportive measures, the risk of non-relapse mortality is a particularly important consideration in older individuals. Sarcopenia, defined as low skeletal muscle mass, has been shown to be associated with decreased overall survival in cancer patients and may identify individuals at higher risk of treatment-related complications.

Methods: Using Mayo Clinic Arizona's hematopoietic stem cell transplantation database, patients aged 60 years or older who underwent allo-SCT between 2008 and 2018 were identified. Patients who underwent abdominal computed tomography (CT) at our institution within 90 days prior to their transplant date were included in the study. The skeletal muscle area (SMA) was obtained using a fully automated algorithm for segmenting abdominal CT images to quantify body composition based on a deep learning approach (Weston et al., Radiology, 2019). The skeletal muscle index (SMI) was then calculated using the SMA and the subject's height at the time the CT was obtained. Sarcopenia was defined based on previously described consensus (Cruz-Jentoft et al., Age Ageing, 2010; Magudia et al., Radiology, 2021). T-tests and Fisher's exact tests compared patient characteristics between groups, where appropriate. Kaplan-Meier methods were used to construct survival times. Log-rank tests compared survival distributions and Cox proportional hazards models estimated hazard ratios.

Results: A total of 79 patients met inclusion criteria (Table 1). Of these, 50 (63%, n=50/79) had sarcopenia, and 29 (37%, n=29/79) had normal skeletal muscle mass. Among the sarcopenia group, 43 (86%, n=43/50) had SMI measurements. No differences were seen between groups in age at transplant, sex, Karnofsky performance scale, disease risk index, or conditioning regimen intent.

There was no statistically significant difference in overall survival between those with sarcopenia and those with normal skeletal muscle mass (log-rank p=0.18). Median survival was 3.3 years (95% CI: 0.8, not estimable (NE)) for those with sarcopenia and 3.6 years (95% CI: 1.3, NE) for those with normal skeletal muscle mass. Given the infrequency of events, the upper bounds of the median survival confidence intervals were not estimable. The unadjusted hazard ratio (HR) for sarcopenia versus normal skeletal muscle mass was 1.65 (95% CI: 0.79, 3.47; p=0.18).

Males had a higher mean SMI than females, as expected (50.4 versus 37.5, p<0.001; mean difference 13.0, 95% CI: 8.9, 17.1). Without considering sex, higher or lower SMI was not associated with survival time in a Cox model in those with sarcopenia (HR: 0.97, 95% CI: 0.92, 1.03; p=0.32). Sex alone was also not associated with any survival benefit among these 43 patients. After adjusting for the difference seen in SMI between sexes, on average, those with higher SMI were associated with a survival benefit (HR: 0.92, 95% CI: 0.84, 0.99; p=0.039). This amounts to roughly an 8% reduction in hazard rate as SMI increased.

Conclusions: The presence of sarcopenia alone was not associated with overall survival in patients 60 years and older undergoing allo-SCT for hematologic malignancy. Rating sarcopenia severity using SMI may assist in identifying high risk individuals with sarcopenia as lower sarcopenia severity was associated with improved overall survival. Further studies are warranted to explore the possible impacts of interventions directed at improving skeletal muscle mass on transplant-related outcomes.

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