Salvage Autologous Stem Cell Transplantation in Daratumumab-Refractory Multiple Myeloma

SIMPLE SUMMARY: Multiple Myeloma (MM) is the most common cancer of the bone marrow and remains incurable despite advances in novel therapy. The disease course is typically characterized by an initial response pattern to treatment followed by eventual relapse and treatment refractoriness. Patients who have progressed on several novel therapies, including the CD38-targeting monoclonal antibody Daratumumab, have a dismal outcome with a median overall survival of less than 10 months and are in dire need of therapies with new mechanisms. While emerging novel modalities have shown promising results, the current study explores the use of high-dose chemotherapy followed by autologous stem cell transplantation (ASCT) in heavily pretreated Daratumumab-refractory MM patients. Our results for 69 consecutive patients treated with salvage ASCT indicate that this approach can lead to long-term MM control and should be considered a treatment modality in selected heavily pretreated Daratumumab-refractory patients. ABSTRACT: Daratumumab, a CD38-targeting monoclonal antibody, has significantly improved survival rates in multiple myeloma (MM), yet patients who progress on Daratumumab have dismal clinical outcomes with an overall median of less than 10 months. While emerging novel modalities have shown promising results, the current study explores the use of high-dose chemotherapy followed by autologous stem cell transplantation (ASCT) in heavily pretreated Daratumumab-refractory MM patients. We retrospectively investigated the outcome of 69 consecutive patients who received upfront ASCT. The median progression-free survival (PFS) for the entire patient cohort was 7.2 months with a median overall survival (OS) of 19.3 months. For patients with ≥very good partial response (VGPR), median PFS and OS improved to 9 months and 34 months, respectively. Achievement of MRD negativity in ≥VGPR did not further improve the outcome. A better performance status, younger age, longer time interval from initial MM diagnosis/initial ASCT to salvage ASCT and low-risk GEP70 were all associated with improved PFS and OS after salvage ASCT. Our results suggest a role for salvage ASCT in selected heavily pretreated and Daratumumab-refractory patients.