Plateau is a prognostic factor of lenalidomide therapy for previously treated multiple myeloma.

Objectives The plateau phase emerging during the treatment of multiple myeloma (MM) is known to last steadily for a certain period, even without treatment. Therefore, the treatment started at plateau phase is expected to be associated with a better outcome. In this study, this hypothesis was evaluated retrospectively for previously treated MM patients in Kansai Myeloma Forum database who received lenalidomide (LEN) with or without dexamethasone for the first time. Method Disease stability index (DSI) was defined as: (maximum - minimum values of M-protein during the 90 days before the start of LEN) divided by M-protein values at the start of LEN. The patients were classified to 3 groups: stable (S), DSI ≤0.25; increasing (I), DSI >0.25 with increasing M-protein; decreasing (D), DSI>0.25 with decreasing M-protein. Outcomes In univariate analysis of 352 patients, DSI, age, non-IgG type, and low albumin were statistically significant prognostic factor for both progression-free survival and overall survival. Multivariate analysis revealed that the median overall survival of the group I was significantly worse compared with that of group S or D (p=0.015). Conclusion DSI is an independent prognostic factor for treatment with LEN for previously treated MM. This article is protected by copyright. All rights reserved.