Efficacy of thalidomide- or lenalidomide-based therapy in proliferative multiple myeloma

Abstract

The proliferative activity of neoplastic plasma cells (PCs) is an independent determinant of the clinical course of patients with multiple myeloma (MM). It can be measured by the plasma cell labeling index (PCLI), which denotes the percentage of bone marrow PCs in the S-phase of the cell cycle.1 Typically, MM is a slow-growing tumor with very few PCs synthesizing DNA at a given time. Proliferative myeloma, characterized by a high PCLI (1%), constitutes nearly a third of all MM cases, and has a poorer outcome.1 Although technical difficulties have limited its widespread application, the slide-based PCLI provides valuable insight into the tumor biology, with higher PCLI predictive of an aggressive course.1, 2, 3 There is a direct correlation between the cytogenetic abnormalities and the rate of PC division perhaps because these chromosomal abnormalities impart a distinct proliferative advantage to the myeloma cells.4 Conversely, it can be argued that rapid PC division leads to sufficient genetic instability to cause secondary chromosomal abnormalities, which adversely affect the prognosis of the patients.