The Merlini, Waldenström, Jayakar staging system revisited

At present, none of the routinely used staging systems is entirely satisfactory, since all of them require some reconsideration to account for the most recent prognostic factors. Among these, serum beta-2 microglobulin (S-beta-2M) has proved to be a powerful prognostic test assessable in most centers. In order to improve the Merlini, Waldenström, Jayakar (MWJ) staging system, we have determined the prognostic significance of several factors in an independent population of 345 retrospective myeloma patients seen at our institution from 1973 to 1988. The Cox regression hazards method showed that S-Creatinine, S-Albumin levels and percentage of bone marrow plasma cells accounted for 94% of total chi 2 achieved with all eight variables (including also: paraprotein index, S-Calcium, S-M-component, bone lesions and hemoglobin). The same analysis, applied to patients in whom S-beta-2M was available at presentation, selected S-beta-2M, S-Creatinine and percentage of bone marrow plasma cells (accounting for 92% of total chi 2), followed by platelet count, S-Albumin and S-M-component. The best discriminatory level of S-beta-2M was found to be 4 mg/l. However, the prognostic power of S-beta-2M when used with binary values was remarkably reduced with respect to its application as a continuous variable. In patients with MWJ stage 1 and 2 disease, S-beta-2M had an independent prognostic significance. Grouping stage I and II patients with S-beta-2M less than or more than 4 mg/l presented a median survival of 70 and 40 months, respectively. In stage 3 patients S-beta-2M did not contribute additional prognostic information.(ABSTRACT TRUNCATED AT 250 WORDS)