Proliferative activity of plasma cells is the most relevant prognostic factor in elderly multiple myeloma patients.
Although multiple myeloma (MM) is predominantly a disease of the elderly, few studies have focused on the identification of prognostic factors in this group of patients. Four hundred twenty five MM patients >65 years were uniformly treated with chemotherapy (MP or VCMP/VBAD). Multivariate analysis identified 4 factors with independent unfavorable prognostic influence: high percentage of S-phase bone marrow plasma cells (>2.5%); elevated beta(2) microglobulin (B2M) (>4 mg/L); age >80 years old; and LDH serum levels (above normal limit). The S-phase value was the most powerful independent prognostic factor to discriminate subgroups of patients with different prognosis. Thus, 3 main risk categories could be identified according to S-phase values: </=1%, 1-3% and >3%, with median survivals of 34, 22 and 12 months, respectively (p < 0.0001). Our study also proved the value for elderly patients of the recently developed International Score System (ISS) based on B2M and albumin. Furthermore, the number of S-phase cells helped to subdivide the ISS III Group identifying a subset of patients with very poor prognosis defined by an additional high S-phase, who displayed a median survival of only 8 months. These results demonstrate that elderly patients can be accurately classified according to prognosis, which may be particularly valuable when comparing the efficacy of new treatment strategies. Moreover, our results underline the high prognostic value of proliferative activity of PC, a parameter that should be considered in routine laboratory investigations of MM.