Myeloablative Conditioning of Patients with Myelofibrosis with Myeloid Metaplasia Using i.v. Treosulfan and Autologous Peripheral Blood Progenitor Cell Transplantation (PBPCT) with High Doses of CD34+ Cells Results in Hematologic Responses - 32 Months Follow-Up of Three Patients and Short-Term Results of a New Study.

Myelofibrosis with myeloid metaplasia (MMM) is a chronic myeloproliferative disorder. Myeloablation with high-dose treosulfan and autologous PBPCT provides a palliative approach. A minimum of 5 x 10⁶ CD34+ cells/kg was collected in all patients after G-CSF-priming (16 μg/kg/d for 4 days). Myeloablation consisted of treosulfan (total dose 42 g/m²). To date we have transplanted 3 patients, all female on an individual basis. We observed a prolonged time to reconstitution of leucocytes > 1/nl post transplantation of 28 days (#1, #2) and 38 days (#3). The observation period post transplantation is 32 months now. Patient #1, who required erythrocyte transfusions twice weekly pretransplant received her last erythrocyte transfusion on day 56; her last Hb-value is 9.5 g/dl. The second patient (#2) recovered to platelet counts higher than pre transplantation (58/nl) at 3 months (143/nl) and had 125/nl at last follow-up. Pat. #3 showed a marked reduction of max. spleen size and a rise in Hb from 9 g/dl to 12 g/dl after 12 months, the last Hb value at 26 months was 7.6 g/dl and she received about 3 erythrocyte transfusions per month again. She then underwent allogeneic transplantation from her sister and is currently alive and well. Three male patients were treated in a new one-armed, multicenter study applying the aforementioned protocol. In two patients we observed again a prolonged reconstitution period of 28 (S1) and 44 (S2) days. In one patient (S1) leukocytosis and thrombocytosis resolved while transfusion dependent anemia persisted. In the second patient (S2) transfusion dependent anemia persisted. He received a backup transplantation but still remains transfusion-dependent. Patient S3 had a critical thrombocytopenia of 16/nl before transplantation and proved to be refractory to thrombocyte transfusions post-transplantation. He developed cerebral hemorrhage and died. The conditioning regimen was well tolerated and despite the prolonged aplasia period neutropenic fever was rare (median 1 day, range 0–6 days). The overall response rate was 60%, the mortality rate was 17% which is both compatible with previous data of autologous transplantation in MMM patients undergoing busulfan conditioning. This multicenter study is continuing to recruit patients (http://leukaemie.krebsinfo.de/kn_home/Studien/studie_101.html).