Baseline physiologic characteristics of participants in the APOLLO ( Personalized rehAbilitation PrOgram in aLLOgeneic Bone Marrow Transplantation) study assessed by MRI: preliminary results

Over 50,000 hematopoietic stem cell transplants (HSCTs) are performed worldwide annually. Patients receiving HSCT for relapsed disease have commonly received prior chemotherapy protocols resulting in reduced physiologic capacity. We have previously shown that treatment-related alterations to muscle/fat distribution and muscle quality significantly reduces physical functioning (VO2peak). Sarcopenic obesity is an independent risk factor of prolonged hospitalization and inferior overall survival in HSCT. In APOLLO, we are utilizing novel MRI techniques studying lean and fat mass in relation to physical performance and quality of life.

to characterize muscle and fat distribution in baseline MRI scans of patients with hematologic diseases participating in the APOLLO study compared to sex-matched normal population.

In the initial 11 participants, quantitative fat and water separated images were used to measure intermuscular fat and muscle volumes from mid-thigh and abdomen were performed. The volumes of muscle, intermuscular, visceral, and subcutaneous fat was measured using custom semi-automated software to identify the boundaries of muscle and the distinct fat groups.

Four females (age 59.5 ± 8) and 7 males (age 67.1 ± 7.5) were included. All were pretreated with a range of 1 – 4 lines of chemotherapy. Compared to our sex-matched healthy control cohort, both females and males had relatively less total thigh muscle volume (5% and 23%) and greater thigh intramuscular fat fraction (17% and 37%). Mean subcutaneous thigh fat in females was 21% lower vs 29% higher in men compared to controls. Abdominal MRI demonstrated 23% less abdominal muscle in women with no difference in males from norms. Abdominal intermuscular fat was 19% greater in women and 52% greater in men. Visceral fat was 21% greater than normal in females and 91% greater in men.

In these preliminary results, prior to undergoing HSCT we observed abnormal patterns and potentially deleterious changes to muscle and fat pools in thigh and abdominal regions. High-intensity drug doses alongside severe deconditioning with prolonged bedfast states would only exacerbate poor body composition and frailty. The high morbidity and mortality rates of HSCT may well be associated with low muscle/ high fat volume distributions, not evaluable without advanced imaging. This work has implications for pre-habilitation in people with high-risk hematologic malignancies, targeted post-HSCT rehabilitation, nutritional studies and other interventions specifically aimed at improving body composition.