Immunophenotypic characteristics and prognostic value of peripheral blood circulating plasma cells in patients with newly diagnosed multiple myeloma.

Background: To investigate the immunophenotypic characteristics and prognostic value of peripheral blood circulating plasma cells (CPCs) in patients with newly diagnosed multiple myeloma (NDMM).

Methods: This retrospective study was conducted on NDMM patients treated at Beijing Chaoyang Hospital, Capital Medical University, between January 2020 and June 2023. A total of 57 patients were included, with a median age of 64 years, comprising 27 males. Forty-four patients were assigned to the higher CPCs group and 13 to the lower CPCs group. To compare the proportion of bone marrow plasma cells (BMPCs) between the two groups and to analyse the differences in the immunophenotypes of BMPCs and CPCs. Subsequently, the prognosis of the patients was analysed by COX.

Results: The percentage of BMPCs was significantly higher in the higher CPCs group compared to the lower CPCs group (53.07% vs. 15.23%, P<0.001). In the higher CPCs group, BMPCs exhibited decreased expression of CD56 and CD27 but increased expression of CD81 (all P<0.05). The median PFS in the lower CPCs group (17.6 months, 9.12-31.54) was significantly higher than that in the higher CPCs group (14.1 months, 5.08-26.12) (P=0.015). Multivariate Cox regression analysis identified CPCs ≥ 0.0101% (HR=6.721, 95% CI: 3.891-11.224, P<0.001) as the independent prognostic factors for PFS.

Conclusions: This study demonstrates distinct immunophenotypic differences between the higher and lower CPCs groups in NDMM patients.