Clinical significance of high-dose chemotherapy with autologous stem cell transplantation in the era of novel agents in patients older than 65 years with multiple myeloma.

High-dose chemotherapy followed by autologous stem cell transplantation (ASCT) is the standard treatment for symptomatic multiple myeloma (MM) in patients under 65 years of age. However, the performing of ASCT in older patients > 65 years without comorbidities or complications is controversial. Introduction of novel drugs, such as daratumumab, has improved the long-term survival of patients with MM who are ineligible for ASCT. This retrospective study aimed to evaluate the clinical significance of ASCT in older patients, even in the era of novel drugs. A total of 55 patients aged 65-74 years (15 ASCT recipients and 40 ASCT-ineligible patients) newly diagnosed with MM between March 2013 and October 2021 at our institution were analyzed in this study. There were no significant differences in the 3-year overall survival (84.6% vs. 90.6%, p = 0.72) and progression-free survival (PFS) (61.2% vs. 75.1%, p = 0.40) between ASCT recipients and ASCT-ineligible patients. There was also no significant difference in complete response (CR) with minimal residual disease (MRD)-negative rate between the two groups (27% vs. 33%, p = 1.0). Multivariate analysis showed that CR was an independent predictor of PFS (hazard ratio [HR], 0.26; 95% confidence interval, 0.08-0.76; p = 0.01). In this retrospective study, despite patients who were determined to be intolerant to ASCT, the non-ASCT group was non-inferior to the ASCT group in PFS and overall response rate. The results of this study confirm that the significance of ASCT is diminishing in patients 65 years of age and older because newer agents can achieve good responses without ASCT.