The impact of myeloma induction therapy on stem cell mobilization and collection: ‘Daratumumab,’ a boon or a bane?

Objectives: Multiple Myeloma (MM) therapy has evolved over many years. While first-line induction therapy has undergone drastic changes, Autologous hematopoietic stem cell transplantation (ASCT) still plays a significant role in consolidation, improving both the depth of response and progression-free survival. Our study aimed at assessing the impact of myeloma induction therapy on stem cell mobilisation and collection. Material and Methods: In our study, data of 29 Myeloma patients who underwent ASCT at SGPGI, Lucknow from 2014 to 2023 was retrospectively analyzed. Patients were stratified into cohorts according to the induction therapy received prior to transplant. Outcomes were compared among cohorts who received prior therapy with Immunomodulatory drugs (Lenalidomide, Pomalidomide) (n=18), Proteosome inhibitors (Bortezomib, Carfilzomib) (n=29) and Monoclonal antibody (Daratumumab) based regimen (n= 5). Also, the dose of stem cell infused was correlated with the day of engraftment of stem cells. The number of induction cycles received prior to transplant were correlated with the use of Plerixafor for mobilization of stem cells. Results: A greater number of stem cell yield was reported in the group who received Immunomodulatory drugs and Proteosome Inhibitors as compared to Daratumumab based therapy. Prior induction regimen with Immunomodulatory drugs did not significantly alter stem cell mobilization (p= 0.707). However, Daratumumab based regimen showed significantly lower yield of stem cells (p <0.001). No significant correlation was noticed between the average number of prior induction cycles and the use of Plerixafor for mobilization of stem cells (p= 0.551). No significant correlation was noticed between the dose of stem cells and the day of engraftment (p= 0.094). Conclusion: Albeit small numbers, this study highlights the fact that treatment with Daratumumab especially in a relapsed, refractory setting impairs stem cell mobilization and warrants larger studies for further correlation.