Characterization of Anthropometric Changes in Patients with Relapsed/Refractory Myeloma Treated with BCMA Bispecific Antibody Teclistamab

Introduction: Cancer-associated cachexia is associated with poor survival rates in several cancer types. Multiple Myeloma (MM) preferentially occurs in the elderly and is the most common cancer that causes lytic bone metastasis causing bone pain, fractures, mobility limitations, and falls. Cachexia is projected to be common in myeloma but has not been fully studied. Myeloma treatments including corticosteroids, radiation and alkylators cause muscle loss, while novel immunotherapy is tumor-specific but their impact on cachexia is unknown. We characterize the changes in body composition in patients with relapsed/refractory myeloma treated with BCMA bispecific antibody teclistamab and determine the association between body composition with treatement response and overall survival. Methods: 49 MM patients treated with teclistamab between 2000 and 2021 were included. All were with relapsed/refractory disease after > 4 lines of therapy and received an approved dose and schedule of teclistamab. The response assessment was according to IMWG criteria. Body weight, body mass index (BMI), tumor burden, and organ function were assessed at baseline and post-treatment. Standard-of-care abdominopelvic CT or PET/CT scans at baseline and at last known follow up were analyzed with Data Analysis Facilitation Suite (DAFS) software to quantify skeletal muscle (SKM), visceral adipose tissue (VAT), and subcutaneous adipose tissue (SAT). Differences between groups were tested using the χ 2 test or paired t-test. Progression free survival (PFS) and overall survival (OS) from the start of teclistamab to progression and death or last follow-up, respectively, were analyzed by the Kaplan-Meier method. Comparisons were made with the log-rank test. Results: Patient characteristics are detailed in Table 1. Based on the WHO definition, 2% were underweight, 16% were normal weight, 19% were overweight and 13% were obese, at baseline. The baseline mean SKM was 105.6 ± 27.8 (Male 122.0 ± 25.3, female 93.4 ± 23.5). SAT and VAT varied widely. Median SAT was 196.5 (range 48.3-558.6), and median VAT was 136.6 (33.09-448.1). Of 32 patients in the obese group, 16 (50%) patients had SKM that was below the mean SKM of the group. Baseline SAT and VAT, but not SKM were correlated with BMI. Twenty-seven of the 49 patients had paired imaging. The absolute changes in skeletal muscle and adipose tissue compartments are shown in Table 2. A majority of patients had a decline in SKM, SAT and VAT post-treatmen