Plateau phase in multiple myeloma: an end-point of conventional-dose chemotherapy

Background and objective. In multiple myeloma (MIM) patients treated with c onventional chemotherapy, the attainment and duration of a plateau phase se ems to affect survival more than the degree of response to initial treatmen t. The aims of this study are: 1) to analyze within a cohort of previously untreated MM patients the incidence and the duration of the plateau phase; 2) to correlate It with the presenting features; 3) to assess ifs impact on survival. Design and Methods A series of 146 consecutive MM patients treated with con ventional chemotherapy were evaluated far this study. Of 146 patients, 102 responded (13 achieving complete response, 21 partial response, and 68 mini mal response), and 44 showed less than minimal response or a progression. A plateau phase was documented in 115 patients (comprising all responders an d 13 non responders. The median plateau phase duration was 21.6 months. The majority of patients received Intermittent cycles of chemotherapy (melphal an or interferon) during the plateau phase. In multivariate analysis, lytic lesions, response, and time to the best response (TBR) correlated with the attainment of a plateau, while stage, response as a whole, and TBR showed a significant correlation with the duration. In contrast, the type of respo nse did not correlate with either the attainment or the duration of plateau . To analyze the prognostic impact of presenting features, response to ther apy and plateau we used a hierarchical model for survival. The analysis sho wed that the response to therapy and the duration of plateau significantly affect the survival. Interpretation and Conclusions In multiple myeloma a plateau phase of at le ast 6 months' duration has a higher impact an survival than the degree of r esponse to conventional chemotherapy so plateau duration could be used as t arget of therapeutic trials. The best way to maintain the plateau phase rem ains, however, undefined. (C) 1999, Ferrata Storti Foundation.