Value of beta 2-microglobulin level and plasma cell labeling indices as prognostic factors in patients with newly diagnosed myeloma.

Beta 2-microglobulin (beta 2M) has been proposed as a prognostic factor in multiple myeloma (MM), but beta 2M levels are reported to correlate with other prognostic indicators such as stage and creatinine level. This study addressed the independent prognostic values of these and other variables, including plasma cell labeling indices (LI), in patients with newly diagnosed MM. beta 2M levels were measured with an enzyme-linked immunosorbent assay. LI were determined with a [3H]thymidine autoradiography method. By multivariate analysis and Kaplan-Meier survival analysis, the uncorrected beta 2M level remained the most significant prognostic factor after adjustment for age. Stage and creatinine level were closely related to beta 2M level and were no longer predictive of outcome after adjustment for age and beta 2M. Plasma cell LI varied independently of beta 2M level and remained predictive. A subset of patients with plasma-blastic myeloma had poor survival since beta 2M level and plasma cell LI were high. By using beta 2M level and LI, three risk groups were defined: low (beta 2M less than 4 micrograms/mL and LI less than 0.4%, median survival 48 months); intermediate (beta 2M less than 4 micrograms/mL and LI greater than or equal to 0.4%, median survival 29 months); and high (beta 2M greater than or equal to 4 micrograms/mL, median survival 12 months). Such grouping may better identify MM patients who might benefit from new treatment regimens.