Brian G.M. Durie

The presenting clinical features of 71 patients with multiple myeloma were correlated with myeloma cell mass (myeloma cells X 10(12)/m2 of body surface area) determined from measurements of monoclonal immunoglobulin (M-component) synthesis and metabolism. Bivariate correlation and multivariate regression analyses showed that myeloma cell mass could be accurately predicted from A) extent of bone lesions, B) hemoglobin level, C) serum calcium level, and D) M-component levels in serum and urine. Analyses of response to chemotherapy and survival indicated significant correlation with measured myeloma cell burden. The results were synthesized to produce a very reliable and useful clinical staging system with three tumor cell mass levels (Table 7). For clinical research purposes, multivariate regression equations were developed to predict optimally the exact myeloma cell mass. Thus, initial staging can be quantitatively related to followup using tumor cell mass changes calculated from changes in M-component production. Use of the clinical staging system sould provide better initial assessment and followup of individual patients, and should lead to improved study design and analysis in large clinical trials of therapy for multiple myeloma.

PURPOSE: There is a need for a simple, reliable staging system for multiple myeloma that can be applied internationally for patient classification and stratification. PATIENTS AND METHODS: Clinical and laboratory data were gathered on 10,750 previously untreated symptomatic myeloma patients from 17 institutions, including sites in North America, Europe, and Asia. Potential prognostic factors were evaluated by univariate and multivariate techniques. Three modeling approaches were then explored to develop a staging system including two nontree and one tree survival assessment methodologies. RESULTS: Serum beta2-microglobulin (Sbeta2M), serum albumin, platelet count, serum creatinine, and age emerged as powerful predictors of survival and were then used in the tree analysis approach. A combination of Sbeta2M and serum albumin provided the simplest, most powerful and reproducible three-stage classification. This new International Staging System (ISS) was validated in the remaining patients and consists of the following stages: stage I, Sbeta2M less than 3.5 mg/L plus serum albumin > or = 3.5 g/dL (median survival, 62 months); stage II, neither stage I nor III (median survival, 44 months); and stage III, Sbeta2M > or = 5.5 mg/L (median survival, 29 months). The ISS system was further validated by demonstrating effectiveness in patients in North America, Europe, and Asia; in patients less than and > or = 65 years of age; in patients with standard therapy or autotransplantation; and in comparison with the Durie/Salmon staging system. CONCLUSION) The new ISS is simple, based on easy to use variables (Sbeta2M and serum albumin), and recommended for early adoption and widespread use.