Abstract
•A subset of multiple myeloma patients achieves a suboptimal response to induction therapy.•Higher disease burden pre-autologous peripheral blood stem cell transplantation (ASCT) confers a poorer prognosis.•Cyclophosphamide-based chemomobilization (CM) does not enhance ASCT long-term outcomes.•Intensive CM with PACE- or HyperCVAD-based regimens boosts event-free survival in a propensity score matching analysis.
Most transplant-eligible multiple myeloma (MM) patients undergo autologous peripheral blood stem cell collection (PBSC) using G-CSF with on-demand plerixafor (G±P). Chemomobilization (CM) can be used as a salvage regimen after G±P failure or for debulking residual tumor burden ahead of autologous peripheral blood stem cell transplantation (ASCT). Prior studies utilizing cyclophosphamide-based CM have not shown long-term benefit.
At our center, intensive CM (ICM) using a PACE- or HyperCVAD-based regimen has been used to mitigate “excessive” residual disease based on plasma cell burden or MM-related biomarkers. Given the lack of efficacy of non-intensive CM, we sought to determine the impact of ICM on event-free survival (EFS), defined as death, progressive disease, or unplanned treatment escalation.
We performed a retrospective study of newly diagnosed MM patients who collected autologous PBSCs with the intent to proceed immediately to ASCT at our center between 7/2020 and 2/2023. Patients were excluded if they underwent a tandem autologous or sequential autologous-allogeneic transplant, had primary plasma cell leukemia, received non-ICM treatment (i.e., cyclophosphamide and/or etoposide), or had previously failed G±P mobilization. To appropriately evaluate the impact of ICM among those who potentially could have received it, we utilized a propensity score matching (PSM) approach whereby ICM patients were compared to a cohort of non-CM patients matched on pre-ASCT factors most strongly associated with the receipt of ICM.
Of 451 patients identified, 61 (13.5%) received ICM (PACE-based, n=45; hyper-CVAD-based, n=16). Post-ICM/pre-ASCT, 11 patients (18%) required admission for neutropenic fever and/or infection. Among 51 evaluable patients, the overall response rate was 31%; however, 46 of 55 evaluable patients (84%) saw a reduction in M-spike and/or involved FLCs. Among those evaluated with longitudinal peripheral blood flow cytometry (n=8), 5 patients (63%) cleared circulating blood PCs post-ICM. Compared to patients mobilized with non-CM, ICM patients collected a slightly greater median number of CD34+ cells (10.8 vs 10.2 × 10⁶/kg, p=.018). The median follow-up was 30.6 months post-ASCT. In a PSM multivariable analysis, ICM was associated with significantly improved EFS (HR 0.30, 95% CI 0.14 to 0.67, p=.003), but not improved OS (HR 0.38, 95% CI 0.10 to 1.44, p=.2). ICM was associated with longer post-ASCT inpatient duration (+4.1 days, 95% CI, 2.4 to 5.8, p<.001), more febrile days (+0.96 days, 95% CI 0.50 to 1.4, p<.001), impaired platelet engraftment (HR 0.23, 95% CI 0.06 to 0.87, p=.031), more bacteremia (OR 3.41, 95% CI 1.20 to 9.31, p=.018), and increased antibiotic usage (cefepime: +2.3 doses, 95% CI 0.39 to 4.1, p=.018; vancomycin: +1.0 doses, 95% CI 0.23 to 1.8, p=.012).
ICM was independently associated with improved EFS in a matched analysis involving MM patients with excessive disease burden at pre-ASCT workup. This benefit came at the cost of longer inpatient duration, more febrile days, greater incidence of bacteremia, and increased antibiotic usage in the immediate post-ASCT setting. Our findings suggest that ICM could be considered for a subset of MM patients, but its use must be weighed carefully against additional toxicity.