Factors influencing hematopoietic stem cell mobilization during autologous stem cell transplantation in patients with hematological malignancies

Background and Objectives Autologous stem cell transplantation (autoSCT) is a cornerstone in the treatment of various haematological malignancies, such as multiple myeloma (MM), Hodgkin lymphoma (HL), and non-Hodgkin lymphoma (NHL). By allowing for high-dose chemotherapy administration followed by haematopoietic stem cell (HSC) rescue, autoSCT significantly improves progression-free and overall survival rates in afflicted patients. This highlights the critical role of HSC mobilization in autoSCT, since yielding a sufficient number of HSCs is vital for transplantation success. However, a subset of patients fails to reach this threshold, resulting in unsuccessful autoSCT. Analyzing the major predictive factors influencing HSC transplantation, can provide valuable insights into the enhancement of mobilization protocols and the optimization of patient outcomes. Therefore, the establishment of distinct predictive factors is key for tailoring effective mobilization strategies. To address this challenge, this study aimed to identify the patient-specific, disease-specific and treatment-specific factors influencing HSC mobilization in patients with malignant diseases undergoing autoSCT, thereby contributing to clinical advancements in mobilization strategies. The assessed parameters consisted of age, gender, comorbidity count, prior radiotherapy, diagnosis, bone marrow plasma-cell infiltration percentage and induction therapy regimens. The objectives for this study were:

1. Investigate patient-specific factors influencing HSC mobilization in autoSCT in patients with malignant hematological diseases.
2. Evaluate disease-specific variables affecting HSC mobilization in autoSCT in patients with malignant diseases.
3. Analyze treatment-related factors predicting HSC mobilization in autoSCT in patients with malignant hematological disorders. Material A retrospective observational cohort study was conducted at the Department of Haematology at the Lithuanian University of Health Sciences Kaunas Clinics. Data from 154 patients diagnosed with Hodgkin lymphoma (HL), non-Hodgkin lymphoma (NHL), or multiple myeloma (MM) were collected from institutional database between 2020 and 2024. The primary outcome variable was the absolute yield of CD34⁺ (i.e., a specific marker for HSCs), cells expressed in ×10⁶ cells/kg. Results The analysis of CD34+ cell yields indicated that mobilization protocols were successful across the cohort, confirming sufficient collection of CD34+ cells for effective autoSCT. The majority of patients achieved CD34+ cell yields well above the minimum threshold of 2 ×10⁶ cells/kg, with only one patient below this range. This highlights the overall efficacy of the applied mobilization strategies, despite the presence of factors known to adversely influence mobilization outcomes. The findings of the study identified age, prior radiotherapy, diagnosis, and certain induction therapies as significant statistical predictors of HSC mobilization outcomes (p-value < 0,05). Two patient-related factors – age and prior radiotherapy – showed a statistically significant negative correlation with CD34⁺ cell yield, as indicated by their respective p-values of 0,0000067 and 0,012. Regarding disease-specific factors, Hodgkin lymphoma (C81.0, p-value = 0,000067), and aggressive T-cell lymphoma (C84.0, p-value = 0,047) demonstrated the strongest association with HSC mobilization – yielding significantly fewer CD34⁺ cells in comparison with other diagnoses. Finally, certain induction therapies – as treatment-related factors – played a pivotal role in mobilization outcomes. DHAP (p-value = 0,0026), MTX-R (p-value = 0,0000047), and Vel-Dex (p-value = 0,023) demonstrated a statistically significant favorable effect on CD34⁺ cell yields. Contrastingly, ICE had a statistically significant negative correlation with CD34⁺ cell yield, with a p-value of 0,021. Conclusions It was concluded that HSC mobilization is a multifactorial process encompassed by specific patient-related, disease-related, and treatment-related factors. The results support the implementation of individualized, patient-centered mobilization strategies. Practical recommendations involve early risk assessment, integration of enhanced mobilization regimens for high-risk patients, and diligent selection of induction therapies in order to optimize mobilization outcomes.