LP-07. Efficiency of autologous hematopoietic stem cell transplantation in patients with multiple myeloma complicated by bone plasmacytomas

Summary

Bone plasmacytoma is a plasma cell tumor that develops in the bone marrow cavities of the skeletal bones and can destroy the cortical layer of the bone, followed by the release of tumor proliferate into the surrounding tissues. Some researchers define a distinct clinical form of multiple myeloma (MM), which occurs with the formation of bone plasmacytomas. However, at present, therapeutic approaches to the treatment of MM complicated by bone plasmacytomas have not been fully developed. Our aim was to determine the frequency of achieving antitumor response after induction and transplantation stages of treatment in patients with MM, depending on the presence of bone plasmacytomas.

Patients and methods

The study included 47 patients with MM aged 26 to 66 years (median 54 years). All patients underwent low-dose CT of the skeletal bones during the diagnosis of the disease. Induction therapy was carried out with bortezomib-containing regimens. In the period from 2019 to 2022, all patients underwent transplantation of autologous hematopoietic blood stem cells (auto-HSCT) in the Department of Hematology and Chemotherapy of Paraproteinemic Hemoblastoses with a BMT and HSC unit of the National Research Center for Hematology of the Ministry of Health of the Russian Federation. The assessment of the antitumor response was carried out in accordance with the IMWG criteria (2016). In patients with bone plasmacytomas, a study of the size of each specific plasmacytoma in dynamics was performed using CT.

Results

According to CT, plasmacytomas weren’t detected in 10 patients, bone plasmacytomas without the release of the soft tissue component beyond the bone were detected in 11 patients, in 26 cases – bone plasmacytomas with the release of the soft tissue component. Table 1 shows the frequency of achieving antitumor response in patients with MM after induction therapy and on day +100 of auto-HSCT, depending on the presence of bone plasmacytomas. Auto-HSCT brought an additional effect and allowed to deepen the antitumor response in all groups of patients. The most impressive results were obtained in patients with bone plasmacytomas with the release of the soft tissue component beyond the bone. After induction therapy, only 19.2% of patients with bone plasmacytomas releasing beyond the bone achieved a very good partial response (VGPR) and a complete response (CR). On +100 day following auto-HSCT, VGPR and CR were already documented in this group in 53.9% of cases. Similarly, in the groups of patients without plasmacytomas and with bone plasmacytomas without external release of the soft tissue component, auto-HSCT made it possible to enhance the antitumor response. I.e., the VGPR and CR rates after the induction stage were documented in 60% and 63.6% of patients. Following hematopoietic cell transplantation, these indexes reached 80% and 81.8%, respectively.

Conclusion

Auto-HSCT is effective in the group of patients with bone plasmacytomas with the release of the soft tissue component beyond the bone: it allowed a 2.5-3-fold increase in the frequency of achieving a deep antitumor response (VGPR and CR).

Keywords

Multiple myeloma, bone plasmacytoma, hematopoietic stem cell transplantation, autologous.