High levels of serum IL-10 indicate disease progression, extramedullary involvement, and poor prognosis in multiple myeloma.

Multiple myeloma (MM) is a common malignant hematological tumor in adults, which is characterized by clonal malignant proliferation of plasma cells in the bone marrow and secretion of a large number of abnormal monoclonal immunoglobulins (M protein), leading to bone destruction, hypercalcemia, anemia, and renal insufficiency (Alexandrakis et al., 2015; Yang et al., 2018). Since a large number of new drugs, represented by proteasome inhibitors and immunomodulators, have been successfully used to treat MM, treatment efficacy and survival of patients have been significantly improved. However, due to the high heterogeneity of this disease, patients have responded differently to treatments with these new drugs (Palumbo and Anderson, 2011; Wang et al., 2016; Huang et al., 2020). Growth and survival of MM cells depend on the bone marrow microenvironment, especially numerous inflammatory cytokines secreted by myeloma cells and bone marrow stromal cells, such as vascular endothelial growth factor (VEGF), interleukin (IL)‍-6, transforming growth factor-‍β (TGF‍‍-‍‍β), and IL-10. These cytokines can promote the growth of myeloma cells, induce angiogenesis, and inhibit antitumor immunity, and are often linked to patient prognosis (Kumar et al., 2017). In this era of new drugs, the prognostic values of the serum levels of these cytokines in MM need further evaluation.