Background: Currently, the standard treatment of MM is a three-drug regimen that includes immunomodulators, corticosteroids, and proteasome inhibitors, followed by an autologous stem cell transplant. Before the introduction of proteasome inhibitors in 2003, the treatment regimen only included immunomodulators and corticosteroids. Due to the high cost of proteasome inhibitors and their unavailability in specific settings, some MM patients are still treated with only a two-drug regimen to date.

Objective: To evaluate the role of autologous hematopoietic stem cell transplants (aHSCT) as consolidation therapy in patients with multiple myeloma (MM) treated with a two-drug regimen (corticosteroid + immunomodulator) or a three-drug regimen (corticosteroid + immunomodulator + proteasome inhibitor), and their overall survival (OS) and progression-free survival (PFS).

Methods: We conducted a retrospective cohort study of patients diagnosed with MM between 1991 and 2025 in a single institution. The diagnosis of MM was based on the International Myeloma Working Group (IMWG) criteria. Patients were grouped into two treatment cohorts: dual therapy (corticosteroid + immunomodulator) and triple therapy (corticosteroid + immunomodulator + proteasome inhibitor). Kaplan-Meier survival analysis and Cox proportional hazards models were used to compare OS and PFS between groups.

Results: The study included 105 patients (two-drug: n = 60; three-drug: n = 45). We detected a statistically significant difference in OS between the two cohorts (median OS: 230.7 months vs. 58.8 months; p = 0.0061). However, PFS did not significantly differ (median PFS: 56.57 months vs. 56.2 months; p = 0.5941). Fifty-one patients received an aHSCT (48.5%), 31 in the dual therapy group and 20 in the triple therapy group. Patients given two drugs and subsequently autografted did better than those given three drugs before the aHSCT. Median OS in the dual-therapy group was 230.7 months, compared to 85.3 months in the triple-therapy group, and this difference was statistically significant (log-rank p = 0.0052). This suggests that adding a PI did not result in an improved overall survival in this cohort. Patients who received an aHSCT did significantly better than those who did not, regardless of whether their medical treatment included a doublet or triplet regimen: the median OS was 189 and 73.76 months in grafted and non-grafted patients, respectively (p= 0.0015).

Conclusion: In this single-institution study, we found that aHSCT as consolidation therapy in MM is equally effective in patients receiving two- or three-drug combination therapy. This observation highlights the importance of aHSCT in the treatment of persons with MM, even in circumstances in which economic restraints preclude triple therapy. These findings underscore the need to adapt therapy in patient-specific settings while reducing treatment costs without compromising efficacy.

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2025
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