Analysis of human myeloma cell population kinetics

Pretreatment plasma cell 3H-thymidine labeling index (LI) was related to chemotherapy response in 37 multiple myeloma patients treated with alkylating agents. Response rate did not significantly differ in patients with high (greater than 3%), intermediate (2-3%) and low (less than 2%) LI values, and survival duration was significantly longer in patients with low LI irrespective of response to chemotherapy. Median response duration was distinctly shorter in patients with high and intermediate values (3 and 11 months, respectively) than in those with low values (30 months; p less than 0.01). LI at relapse was similar to that found at presentation in 5 out of 10 patients studied but was sharply increased in the other 5 who had an aggressive clinical course following initial response. Four of these latters showed a clonal evolution of bone marrow plasma cells, detected by changes in cell ploidy at flow-cytometric analysis.