Impact of pomalidomide-containing induction chemotherapy on hematopoietic stem cell mobilization in multiple myeloma: A retrospective cohort study

Introduction Pomalidomide (POM), a potent immunomodulatory agent, is increasingly used in multiple myeloma (MM). Preclinical data suggest POM upregulates CXCR4 on hematopoietic stem cells (HSCs), potentially impairing mobilization, similar to lenalidomide (LEN). However, clinical evidence on POM's effect on stem cell collection remains limited. This study evaluated the impact of POM-containing induction regimens on HSC mobilization outcomes in transplant-eligible newly-diagnosed MM (TE-NDMM) patients. Methods We conducted a retrospective cohort study of TE-NDMM patients undergoing stem cell mobilization (Jan–Nov 2024). Inclusion: (1) Confirmed TE-NDMM; (2) Completed induction and mobilization. Exclusion: No mobilization attempt. Patients were stratified by induction regimen: POM-exposed (POM group, n=33) vs POM-unexposed (non-POM group, n=51). Mobilization used G-CSF ± plerixafor ± high-dose cyclophosphamide (HD-CTX). Primary endpoint: Poor mobilizer (PM) incidence (defined as ≥3 apheresis sessions or ≥2 plerixafor doses). Secondary endpoints: total CD34+ cells/kg collected, plerixafor utilization, and apheresis sessions. Results All 84 patients successfully mobilized in a single attempt. Key findings:PM Incidence: Higher in POM vs non-POM groups (27.3% vs 17.6%, p=0.31), though statistically nonsignificant.CD34+ Yield: Comparable between groups (median 5.2 × 10⁶/kg [POM] vs 5.6 × 10⁶/kg [non-POM], p=0.45).Plerixafor Use: Increased trend in POM group (45.5% vs 33.3%, p=0.28).Dara Exposure: Significantly increased plerixafor need (58.8% vs 32.1%, p=0.02) and apheresis sessions (median 2 vs 1, p=0.01).Negative Predictors of Mobilization: - Increased induction cycles (r = +0.34, p<0.01 for apheresis sessions) - Higher number of induction agents (r = +0.29, p=0.01 for plerixafor doses) - Older age (r = −0.26, p=0.02 for CD34+ yield) Conclusion POM-containing induction is associated with a nonsignificant increase in PM incidence and plerixafor utilization but does not compromise final CD34+ yield. Daratumumab exposure significantly impairs mobilization efficiency. Older age, prolonged induction, and multi-agent regimens negatively impact stem cell harvest. These findings support routine use of HD-CTX or plerixafor for POM-exposed patients and highlight the need for risk-adapted mobilization strategies in TE-NDMM.