P-352: Impact of Obesity on Outcomes of Multiple Myeloma Patients Undergoing Upfront Autologous Stem Cell Transplant

Introduction: Upfront autologous hematopoietic stem cell transplantation (auto-HCT) is standard of care for eligible patients with multiple myeloma (MM). Obesity is a rising global health concern and small cohort studies have had conflicting results regarding its impact on outcomes of MM patients undergoing auto-HCT. We evaluated the impact of body mass index (BMI) on survival outcomes of patients with MM undergoing upfront auto-HCT.

Methods: In this single-center retrospective study, we included patients undergoing upfront auto-HCT between 2000-2021. We evaluated differences in outcomes between patients with normal BMI (18.5 – 24.9 kg/m², BMI-N) and those with high BMI (≥25kg/m², BMI-H). Ten patients (0.4%) were underweight (BMI< 18.5 kg/m²) and were excluded from the analysis. Primary endpoints were progression-free survival (PFS) and overall survival (OS).

Results: A total of 2785 patients were included in our analysis. Six hundred and nine (22%) patients were in the BMI-N group and 2176 (78%) were in the BMI-H group. Within the BMI-H group, 1094 (50%) patients were overweight (BMI 25-29.9 kg/m²), 668 (31%) were moderately obese (BMI 30-34.9 kg/m²) and 414 (19%) were severely obese (BMI ≥35kg/m²). Median age of patients in the entire cohort was 61 years (range 25-83). The most common induction regimen was bortezomib, lenalidomide and dexamethasone (VRD), used in 758 (27%) patients.

Patients in the BMI-H group were more likely to be male (63% vs 45%, p< 0.001), younger (median 60 vs 62 years, p< 0.001), black (19% vs 15%, p=0.012) and to have a higher comorbidity burden (26% vs 16% HCT-CI >3, p< 0.001), yet were less likely to have R-ISS III disease (8% vs 14%, p=0.002), compared to those in the BMI-N group. Patients in the BMI-H group more often achieved a response of ≥VGPR prior to auto-HCT (53% vs 48%, p=0.017) and had a higher rate of pre-transplant MRD negativity (43% vs 37%, p=0.023).

After a median follow-up of 53.8 months, median PFS was 41.0 months (95% CI 38.6, 43.9) and 38.6 months (95% CI 34.6, 43.5) for patients in the BMI-H and BMI-N groups, respectively. Median OS was 101.5 months (95% CI 96.1, 106.2) and 113.3 months (95% CI 98.6,128.3) for patients in the BMI-H and BMI-N groups, respectively. In multivariable analysis, elevated BMI was not associated with either PFS (HR 0.95 [95% CI 0.85, 1.07], p=0.40) or OS (HR 1.15 (95% CI 0.97, 1.36], p=0.11).

Conclusions: In a large cohort of patients undergoing auto-HCT for MM, elevated BMI was not associated with a significant difference in survival outcomes. Our findings suggest that obesity may not be a significant determinant in auto-HCT eligibility for myeloma patients.