High serum IL-2 levels are predictive of prolonged survival in multiple myeloma.

In this study we analysed serum IL-2 levels in 61 patients with multiple myeloma (MM). Patients serum IL-2 levels were significantly higher than normal controls. Moreover, higher serum IL-2 levels were associated with a prolonged actuarial survival. In particular, 87% of the MM patients with IL-2 greater the or equal to 10 U/ml are still alive at 5 years while only 13% of the remaining patients with IL-2 less than 10 U/ml are alive. The multivariate analysis confirmed these data indicating that high serum IL-2 levels are the most useful predictor index of longer survival in MM patients. Furthermore, among the 50 patients in whom serum beta-2-microglobulin (SB2M) determination was available we observed that all patients with serum IL-2 levels greater than or equal to 10 U/ml had SB2M less than 6 micrograms/ml, whereas in patients with serum IL-2 less than 10 U/ml SB2M ranged from 1.3 to 15 micrograms/ml. Using these two parameters we were able to identify three groups of patients with different survival duration. Group A (9 patients) defined by serum IL-2 greater than or equal to 10 U/ml and SB2M less than 6 micrograms/ml in which all patients are alive: group B (26 patients) characterized by serum IL-2 less than 10 U/ml and SB2M less than 6 micrograms/ml in which 24% of patients are alive and group C (15 patients) characterized by serum IL-2 levels less than 10 U/ml and SB2M greater than or equal to 6 micrograms/ml in which the actuarial survival curve drops to 0 at 2.5 years. A statistically significant difference was observed between groups A and B (P less than 0.05), groups A and C (P less than 0.01) and groups B and C (P less than 0.01). These data could reflect the existence of an active T cell control on B cell neoplasia and may suggest the opportunity of a more extensive use of recombinant biological modifiers such as IL-2 in the therapeutic strategy of MM.