Background and methods: A characteristic of acute myeloid leukemia is the frequent ability of the leukemic cells to sustain their own proliferation in vitro. To determine the clinical importance of this property, we measured the uptake of tritiated thymidine by leukemic cells in serum-free and cytokine-free cultures as a means of determining the rate of spontaneous proliferation in 114 patients with newly diagnosed acute myeloid leukemia. Proliferation was then classified according to three quantitative levels of activity and related to overall survival and to treatment outcome (the response to treatment, the actuarial probability of relapse, and disease-free survival) in 91 patients who were treated with chemotherapy to induce remission.
Results: Of the 114 patients, 37 had low, 39 had intermediate, and 38 had high levels of proliferation. The probability of survival at three years was 36 percent among patients with low levels of proliferative activity and 3 percent among those with high levels (P < 0.001). Among the patients treated with chemotherapy, those with low rates of proliferative activity had a 68 percent rate of complete remission and a 49 percent probability of remaining free of relapse, whereas those with high rates of proliferative activity had only a 39 percent rate of complete remission (P = 0.04) and an 11 percent probability of remaining in complete remission (P = 0.009). The probability of disease-free survival at three years among the patients in complete remission after chemotherapy was 49 percent among those with low rates of proliferative activity and 9 percent among those with high rates (P = 0.004). Accordingly, patients with low rates of proliferative activity also had a significantly higher rate of overall survival (44 percent vs. 4 percent; P = 0.002). Patients whose cells had intermediate levels of proliferation in vitro had intermediate rates of survival, relapse, and disease-free survival.
Conclusions: The capacity of leukemic blasts for autonomous proliferation is associated with highly aggressive acute myeloid leukemia.