Residual juvenile chronic myelogenous leukemia cells detected in peripheral blood during clinical remission

At diagnosis peripheral blood (PB) or bone marrow from patients with juvenile chronic myelogenous leukemia (JCML) have shown two reproducible abnormalities when studied in cell culture: impaired growth of normal hematopoietic progenitors and excessive proliferation of malignant monocyte-macrophage elements. We used these findings to assess quality of treatment response by serially studying PB specimens from JCML patients (patients 5, 7, 8, and 9) in complete chemotherapy-induced remission. PB readily yielded high numbers of monocyte-macrophage colonies in CFU-C and CFU-GEMM assays when cultured in early remission, and the colonies were cytogenetically proven to have arisen from a malignant clone in patient 9. When studied later in remission, the abnormal cell proliferation persisted in three of the four patients, but in patient 8 PB colony growth resembled controls. Similarly, when PB from patient 8 was studied in liquid culture without using added growth factor, cell proliferation declined identical to controls, whereas PB from the other three patients showed exuberant growth of monocyte-macrophage elements. Patient 8 successfully completed therapy and has been in a long-term, disease-free remission. The other three had recurrent, ultimately fatal disease. The cell cultures have allowed detection of residual abnormal cells that circulate in PB of JCML patients in remission. Although patient numbers were small because of the rarity of JCML, the data suggested that persistence of leukemia cells in these patients had a bearing on clinical outcome.