Prognostic value of serum M-protein doubling time at escape from plateau of multiple myeloma. The Finnish Leukaemia Group.

A long plateau phase is one of the strongest signs predicting long survival in multiple myeloma. The kinetics of escape from the plateau is, however, poorly known, and so is its influence on subsequent survival. During a 9-yr follow-up of 432 myeloma patients the serum M-protein doubling time at first relapse was measured from serial observations in 137 cases. Univariate and multivariate analyses of pretreatment characteristics and of characteristics associated with chemotherapy were used to identify the predictors influencing on M-protein doubling time. In 65 patients the M-protein doubling time was 6 months or less and in 72 longer, with median remaining survival times of 17 and 45 months, respectively; 50% of the former group had any response to salvage chemotherapy, compared to 75% of the latter group. In univariate analysis stage and Hb were significant predictors for the M-protein doubling time. An at least 75% response was associated with short doubling time. However, the multivariate analysis left only a long preceding plateau and use of several drug combinations during primary chemotherapy as significant predictors for a long M-protein doubling time. A M-protein doubling time of 6 months or less is associated with frequent resistance to salvage chemotherapy and short remaining survival. A short doubling of the M-protein is preceded by a short plateau. The use of several drug combinations during primary chemotherapy does not jeopardize the later course of the disease. A short M-protein doubling time seems not be a chemotherapy induced phenomenon.