Similar survival outcomes in patients with biclonal versus monoclonal myeloma: a multi-institutional matched case-control study

Multiple myeloma is a plasma cell malignancy characterized by clonal proliferation of plasma cells in the bone marrow and associated organ damage. Usually, patients with myeloma present with a single monoclonal protein in serum and/or urine constituted by one heavy chain and one light chain. In less than 5% of the patients, more than one monoclonal protein can be identified. The aim of our retrospective multicenter matched case-control study was to describe the characteristics of cases with biclonal myeloma and compare them against a control group of monoclonal myeloma patients matched by age, sex, and year of diagnosis. A total of 50 previously untreated cases with biclonal myeloma and 50 matched controls with monoclonal myeloma were included in this study. The controls were matched (1:1) for age, sex, year of diagnosis, and participating center. There were no differences in the rates of anemia (52 vs. 59%; p = 0.52), renal dysfunction (36 vs. 34%; p = 0.83), hypercalcemia (9 vs. 16%; p = 0.28), or presence of lytic lesions (23 vs. 16%; p = 0.38) between groups. Similarly, there was no difference in the rates of overall response to therapy (85 vs. 90%; p = 0.88) or survival rates of cases with biclonal myeloma and controls with monoclonal myeloma (4-year survival 72 vs. 76%; p = 0.23). Results of our study suggest that patients with biclonal myeloma have similar response and survival rates than patients with monoclonal myeloma.