Prognostic factors and clinical characteristics of patients with newly diagnosed non-secretory multiple myeloma in the era of new drugs in "real-world" study: Experiences of the Polish Myeloma Group.

Background: Non-secretory multiple myeloma (NSMM) accounts for approx. 2-3% of multiple myeloma (MM) cases. Due to the rare occurrence and ineligibility of patients with NSMM to participate in clinical trials, we have limited data on treatment efficacy and the clinical course in these patients. Most of the literature consists of case reports and small retrospective studies.

Objectives: The study aimed to analyze patient characteristics, prognostic factors and treatment outcomes in newly diagnosed (ND) NSMM.

Material and methods: This is a multicenter, retrospective analysis of 43 patients with NSMM diagnosed between June 2010 and September 2021, conducted in 8 Polish hematology centers.

Results: The median overall survival (OS) was 103 months (95% confidence interval (95% CI): 20-72). The most common cause of death was MM disease progression. The overall response rate (ORR) was 84.6%; complete response (CR), very good partial response (VGPR), partial response (PR), and no response (NR) rates were 20.5%, 46.2%, 17.9%, and 15.4%, respectively. In multivariable analysis, factors contributing to worse OS included International Staging System stage 3 (ISS-3) (p = 0.0277), anemia (Hb <10 g/dL or >2 below upper limit of normal value (ULN), p = 0.0270), renal insufficiency (RI, serum creatinine >2 mg/dL, p = 0.0476), and serum albumin <5.5 mg/L (0.0408).

Conclusions: Non-secretory multiple myeloma is a rare subtype of MM. This small study demonstrates that outcomes are comparable to secretory MM. However, the inclusion of this subset of patients in clinical trials is essential to assess prognosis, treatment efficacy and clinical outcomes.