[Prognostic effect of beta 2-microglobulin in multiple myeloma].

BACKGROUND: The aim of the present study was to compare the prognostic influence of beta 2-microglobulin (B2M) corrected according to renal function versus the uncorrected form and relate these values with other characteristics of the disease in a series of patients with multiple myeloma (MM). METHODS: The serum levels of B2M were determined by the radioimmunoassay method (RIA) in 107 patients with newly diagnosed MM and the prognostic influence of B2M was statistically evaluated with univariant and multivariant analysis. RESULTS: The mean value of B2M obtained in patients with MM was 7.8 +/- 8.0 micrograms/ml, with a median of 5 micrograms/ml. Ninety percent of the patients studied presented serum values of B2M higher than the normal limit. The value of B2M corresponding to the median of the series (5 micrograms/ml) separated two groups of patients with different survival (48 vs 19 months) (p = 0.0001). Similarly, the most discriminative value of corrected B2M in agreement with creatinine (2.5 micrograms/ml) permitted the differentiation of two groups of patients although the differences in survival were less significant (36 vs 26 months, p = 0.03) demonstrating its lesser influence as a prognostic factor with respect to the uncorrected B2M. In contrast, a significant association was observed between high values of B2M and Bence Jones myeloma, clinical stage III, anemia, renal failure and intense involvement of the general state. Multivariant analysis demonstrated that B2M plays a greater prognostic role when used as a discrete rather than a continuous variable and that together with the degree of involvement of the general state, serum albumin and the proportion of plasma cells in the bone marrow, they make up the best set of variables for the prediction of prognosis in patients with MM. CONCLUSIONS: Beta 2-microglobulin is one of the most important independent prognostic factors in multiple myeloma with its prognostic value being greatest when used uncorrected according to the values of creatinine.