BACKGROUND
Multiple myeloma, an incurable plasma cell malignancy, has an average age of diagnosis over 65 years. For transplant-eligible patients, high-dose melphalan 200 mg/m2 (MEL200), followed by autologous stem cell rescue (ASCR) is the standard in consolidation therapy. Most clinical trials evaluating MEL200 with ASCR excluded patients over 65 due to concerns for toxicity and treatment-related mortality, leading to use of reduced dose melphalan 140 mg/m2 (MEL140) in clinical practice for older patients. As this dose has limited studies surrounding its reduction, the purpose of this study was to compare outcomes and toxicities of MEL140 in patients over the age of 65 to MEL200 in patients 65 and under.
METHODS
This single-center institutional review board approved retrospective study was conducted at VA Tennessee Valley Healthcare System. All multiple myeloma patients greater than 18 years of age who received melphalan with ASCR from January 1, 2018, to December 31, 2021, were included. Patients were divided into two arms: age < 65 treated with MEL200 and age >65 treated with MEL140. The primary endpoint was oneyear progression-free survival (PFS). The secondary endpoints were one-year overall survival (OS), treatment related mortality, time to neutrophil engraftment, and toxicities including febrile neutropenia, diarrhea, mucositis, infection, and intensive care unit transfers.
RESULTS
A total of 222 patients were included, 114 patients in the MEL200 arm and 108 patients in the MEL140 arm. The primary endpoint of one-year PFS had no significant difference, with 103 (90.4%) patients in the MEL200 group compared to 99 (91.7%) patients in the MEL140 group (p=0.732). Similarly, there was no statistically significant difference in the secondary endpoint of one-year OS with 112 (98.3%) patients in the MEL200 group compared to 106 (98.2%) in the MEL140 group (p=0.956). Toxicities were similar; however, grade 3 mucositis was higher in the MEL200 arm.
CONCLUSIONS
Our study found no difference in oneyear PFS or one-year OS when comparing MEL140 to MEL200 with minimal differences in regimen-related toxicities. Although not powered to detect statistical difference, results suggests that dose reduction with MEL140 in patients >65 years does not impact one-year PFS when compared to patients <65 receiving standard MEL200.