Intramuscular Adipose Tissue Content Predicts Patient Outcomes after Allogeneic Hematopoietic Stem Cell Transplantation

•Lower pretransplantation quality of skeletal muscles, as demonstrated by low radiographic density (RD), can be a risk factor for poor overall survival following allogeneic hematopoietic stem cell transplantation.•A simultaneous decline in RD and the 6-min walking distance test is an independent risk factor for higher nonrelapse mortality, and RD should be included in pretransplantation screening. During clinical courses involving treatment with allogeneic hematopoietic stem cell transplantation (allo-HSCT), multidisciplinary patient assessment including physical function is indispensable, and quantitative skeletal muscle loss is a poor prognostic marker. Deteriorating quality of muscle from intramuscular adipose tissue degeneration can be important as well, because many patients are cachexic or sarcopenic before allo-HSCT, although this approach has not yet been used in such patients. We conducted this retrospective cohort study to evaluate the quality as well as quantity of skeletal muscle using computed tomography (CT) scans. The psoas muscle mass index (PMI) and radiographic density (RD) calculated by cross-sectional area and averaged CT values of the psoas major muscle at the umbilical level were used to determine the quantity and quality of muscle, respectively. A total of 186 adult patients, ranging in age from 17 to 68 years (median, 49 years), were included in this study, with 46 (24.7%) assigned to the lower PMI group and 49 (26.3%) assigned to the lower RD group. Low RD was identified as an independent risk factor for poor overall survival after allo-HSCT (adjusted hazard ratio [HR], 2.54; P < .01), whereas PMI was not significant. Decreased RD along with a reduced 6-min walking distance before transplantation were significant factors in increased nonrelapse mortality (HR, 2.69; P = .01). This study is the first to suggest the use of a qualitative skeletal muscle index to serve as a prognostic indicator following allo-HSCT. RD should be included in pretransplantation screening parameters, and approaches that include rehabilitation focused on improving both muscle quality and quantity may improve the prognosis of allo-HSCT.