Significance of increased blastic-appearing cells in bone marrow following myeloablative unrelated cord blood transplantation in adult patients.

An abnormal increase of nonleukemic blastic-appearing lymphocytes in bone marrow (BM) specimens has been reported after unrelated cord blood transplantation (UCBT). This study analyzed the incidence, chronology, biological features, and clinical significance of elevated numbers of these cells in a series of 165 consecutive adult patients demonstrating myeloid engraftment after myeloablative UCBT in a single institution. The patients' BM samples were routinely evaluated by cytomorphology at different time points after UCBT. When ≥5% of blastic-appearing cells were detected by cytomorphology in the BM, samples were also evaluated by multiparametric flow cytometry to characterize these cells. Systematic chimerism analyses of BM samples using PCR amplification of short tandem repeat markers were performed. Forty-three patients (cumulative incidence, 26.1%) demonstrated ≥5% of nonmalignant blastic-appearing cells in BM after a median of 101 days after UCBT (range, 28-377 days). All of these patients had full-donor chimerism and a clinical course without leukemic relapse. Multiparametric flow cytometry analyses performed in 36 of the 43 patients showed a polyclonal expansion of B lymphocytes with a broad spectrum of maturation stages. An increased number of nonmalignant blastic-appearing cells was significantly associated with a high number of lymphocytes infused at the time of UCBT and with low rates of acute and chronic extensive graft-versus-host disease, suggesting a potential immunoregulatory role of these cells. The observation of ≥5% nonmalignant blastic-appearing cells in BM samples after myeloablative UCBT is frequent, and these should be distinguished from malignant blasts.

Central nervous system involvement at first relapse in patients with acute myeloid leukemia.

The risk factors for and incidence of central nervous system involvement at first relapse in adult patients with acute myeloid leukemia have not been established. This single-center study analyzed the prognostic factors for and cumulative incidence of meningeal relapse in 458 adult patients achieving complete remission. Before 1990, patients received old chemotherapy approaches without stem cell transplantation that often included prophylactic intrathecal chemotherapy. Since 1990, modern protocols included stem cell transplantation without intrathecal prophylaxis. Meningeal relapse occurred in 6 patients (overall 5-year cumulative incidence 1.3%). The 5-year cumulative incidence of meningeal relapse in patients treated with old and modern protocols were 3.9% and 0.3%, respectively. Univariate and multivariate analyses showed that the chemotherapy approach was the main prognostic factor for central nervous system relapse (P=0.02). This study shows an extremely low incidence of meningeal relapse in adult patients with acute myeloid leukemia treated with modern protocols including stem cell transplantation without intrathecal prophylaxis.