nThe Effect of Conditioning Regimen Dose Reduction in Obese Patients Undergoing Autologous Hematopoietic Cell Transplantation.

There are limited data on whether to adjust high-dose chemotherapy prior to autologous hematopoietic cell transplant (autoHCT) in obese patients. This study explores the effects of dose adjustment on the outcomes of obese patients, defined as body mass index (BMI) ≥ 30 kg/m2 . Dose adjustment was defined as a reduction in standard dosing of ≥ 20%, based on ideal, reported dosing and actual weights. We included two groups of US patients who had received autoHCT between 2008 and 2014. Specifically, we included patients with multiple myeloma (MM, n=1696) treated with high-dose melphalan; and we included patients with Hodgkin or non-Hodgkin lymphomas (n=781) who received carmustine, etoposide, cytarabine, and melphalan (BEAM) conditioning. Chemotherapy dose was adjusted in 1324 (78%) patients with MM and 608 (78%) patients with lymphoma. Age, sex, BMI, race, performance score, co-morbidity index, and disease features (stage at diagnosis, disease status and time to transplant) were similar between dose groups. In multivariate analyses for MM, adjusting for melphalan dose and for center effect had no impact on overall survival (p=0.894) and treatment-related mortality (TRM) (p=0.62), progression (p=0.12), and progression-free survival (p=0.178). In multivariate analyses for lymphoma, adjusting chemotherapy doses did not affect survival (p=0.176), TRM (p=0.802), relapse (p=0.633) or PFS (p=0.812). No center effect was observed in lymphoma. This study demonstrates that adjusting chemotherapy dose prior to autoHCT in obese patients with MM and lymphoma does not influence mortality. These results do not support adjusting chemotherapy dose in this population.