Quantitative and Qualitative Changes in Skeletal Muscle Following Haematopoietic Stem Cell Transplantation

Background Although haematopoietic stem cell transplantation (HSCT) is known to cause substantial declines in muscle strength, changes in skeletal muscle quantity and quality remain poorly characterized. The clinical utility of non‐invasive muscle assessment tools, such as bioelectrical impedance analysis (BIA) and ultrasound (US) imaging, has not been systematically compared with computed tomography (CT), which is regarded as the gold standard for skeletal muscle assessment. Methods This study included 31 patients who underwent HSCT (23 allogeneic, 8 autologous; 42% female; median age 47 years). Skeletal muscle mass and quality were assessed using CT, BIA, and US imaging. CT was performed before transplantation, while BIA, US imaging, and physical performance assessments (handgrip strength, knee extension strength, and 6‐min walk test) were conducted both before transplantation and at discharge. Correlations between CT and non‐invasive assessments were analysed, and longitudinal changes in muscle parameters were evaluated. Results BIA‐derived skeletal muscle index and lower‐limb muscle mass showed strong correlations with CT‐based psoas muscle volume ( ρ > 0.75, p < 0.001). CT‐based psoas muscle density demonstrated moderate correlations with phase angle and muscle echo intensity ( ρ = −0.47 to 0.41, p < 0.05). In patients undergoing allogeneic HSCT, significant declines were observed in hydration‐adjusted lean body mass (mean change −2.1 kg, p = 0.024), lower‐limb muscle mass (−0.5 kg, p = 0.005) and rectus femoris + vastus intermedius thickness (−3.5 mm, p = 0.004), phase angle (−0.6°, p < 0.001), handgrip strength (−4.4 kg, p < 0.001), knee extension strength (−72.7 N, p < 0.001), and 6‐min walk distance (−93.7 m, p < 0.001). In contrast, patients undergoing autologous HSCT largely preserved muscle strength and mass ( p > 0.200), despite similar reductions in phase angle (−0.6°, p = 0.001). Conclusions BIA provides a clinically feasible and reliable alternative to CT for assessing skeletal muscle quantity in patients undergoing HSCT. Loss of skeletal muscle mass was strongly associated with functional decline in recipients of allogeneic HSCT, while changes in muscle quality, such as reductions in phase angle, appeared to have limited functional impact. These findings highlight the usefulness of non‐invasive monitoring and suggest that interventions focusing on muscle mass preservation may improve physical function after HSCT.