RESUMO
BACKGROUND: Multiple myeloma (MM) is an incurable hematologic malignancy characterized by the neoplastic proliferation of plasma cells, which produce monoclonal immunoglobulin that can cause vital organ damage, subsequently leading to significant morbidity and mortality. Autologous hematopoietic stem cell transplant (ASCT) is the standard-of-care management of eligible patients with newly diagnosed MM. Experts recommend collecting enough stem cells upfront to support a possible tandem transplant, salvage ASCT, or a stem cell "boost" to allow for the administration of multiagent cytotoxic chemotherapy in patients with relapsed/refractory disease. OBJECTIVE: There is currently a paucity of data on the response rates and outcomes of patients with relapsed MM who undergo cytotoxic chemotherapy followed by a stem cell boost; this study examines the outcomes of patients treated with this approach. METHODS: We conducted a retrospective chart review from two oncologic treatment centers in the United States of adult patients who underwent a first ASCT between 1999 and 2021 and subsequently received cytotoxic chemotherapy followed by stem cell boost further on in their disease course. Survival analysis was carried out using the Kaplan-Meier method, and the log-rank test was used to compare survival curves. RESULTS: We found that the majority (56.6%) of these patients responded to therapy and that 60.6% of these patients were able to receive at least one subsequent line of therapy post-boost. Furthermore, patients who responded to therapy had significantly longer median overall survival compared to those who did not respond (323 days vs 93 days, p=0.0045), and age did not affect response to therapy. CONCLUSION: This data allow clinicians to appropriately implement and inform patients of the therapeutic uses and clinical outcomes of stem cell boost in patients with multiply relapsed/refractory MM.
RESUMO
Salvage autologous hematopoietic stem cell transplantation (HSCT) is an effective treatment for patients with relapsed multiple myeloma (MM). Peripheral blood stem cells (PBSCs), a source of hematopoietic stem cells (HSCs), are collected before the first transplantation, and adequate quantities of PBSCs can be collected and stored potentially for years to support at least 2 transplantations for eligible patients. To ensure the safety of salvage HSCT in the treatment of patients in subsequent relapse, PBSCs must retain the potential to engraft even after several years of cryopreservation. Although PBSC viability has been studied extensively using in vitro techniques, few publications describe the most rigorous functional potency measure, of patients receiving a myeloablative conditioning regimen. This study describes a large single-institution experience evaluating the engraftment kinetics of PBSCs used in salvage transplantation after multiple years of storage compared with first transplantation for the same patients in the treatment of MM. A retrospective chart review of patients with MM undergoing HSCT between 2000 and 2021 identified 89 patients who received salvage autologous PBSCs stored for >1 year after first HSCT. PBSCs were cryopreserved and stored in vapor-phase liquid nitrogen refrigerators at ≤-150°C. All patients received a PBSC product from the same collection cycle for both transplantations. Differences in CD34+ cell doses and days to engraftment between the first and salvage transplantations were tested using the paired 2-tailed t-test and Wilcoxon signed-rank test. Univariate and multivariable linear regressions were used to determine the association between storage time and days to engraftment, adjusting for CD34+ cell dose and conditioning regimen in the multivariable model. The median duration of storage between the day of initial collection and salvage transplant was 5.4 years (range, 1.0 to 19.7 years). Engraftment kinetics demonstrated a sustained neutrophil engraftment (absolute neutrophil count >0.5 × 109 cells/L) at a median of 11 days after both the first and salvage transplantations (range, 8 to 15 days and 8 to 19 days, respectively; P < .05). The median time to sustained platelet engraftment (>20 × 109 cells/L without transfusion support) was 13.5 days after the first HSCT and 14 days after salvage HSCT (range, 9 to 27 days and 10 to 56 days, respectively; P = .616). After adjusting for CD34+ cell doses and conditioning regimens, there was no association between the duration of cryopreservation and days to neutrophil engraftment (r = 0.178, P = .130) or platelet engraftment (r = 0.244, P = .100). Engraftment kinetics of the salvage HSCT are comparable to those of the first HSCT even when products are stored in vapor-phase nitrogen refrigerators for a median of 5.4 years. There is no association between the duration of storage and time to engraftment when controlling for CD34+ cell dose and conditioning regimen. Prolonged storage of cryopreserved HSC products is a safe practice for MM patients undergoing salvage autologous HSCT.