Primed-G-CSF BMT for Children with Fanconi Anemia (FA) Using Mycophenolate Mofetil (MMF) and Cyclosporine-A for Gvhd Prophylaxis: Rapid Neutrophil Engraftment, Less Mucositis and Low Incidence of Chronic Gvhd

Abstract 3522

Given the historically poor outcomes with standard-dose cyclophosphamide (Cy), preparative regimens for FA have been modified significantly with the goal of limiting toxicity while maintaining engraftment. The most frequently used preparative regimen for patients with bone marrow failure due to FA undergoing matched related HSCT is low dose of Cy.

Primed-GCSF BMT (G-BMT) has shown to result in rapid neutrophil recovery and lower incidence of chronic GVHD in comparison to PBSCT likely due to the harvest of higher number of CD34+ cells and a lower number of lymphocytes. In addition, the use of MMF instead of methotrexate (MTX) for GVHD prophylaxis can decrease both severity of mucositis and hematological toxicities.

From April 2003 to December 2009, 10 children with bone marrow failure due to FA were transplanted in our center. The patients were 3 females and 7 males, with a median age of 10 years (range, 4 to 15 years). FA was diagnosed based on clinical and radiological findings as well as a positive DEB test. The median time between the diagnosis of bone marrow failure due to FA and BMT was 24 months (range, 6 to 48 months). The protocol was approved by our institutional review board and informed consent was obtained from each patient and donor and or their guardians.

Half of these patients had previously been treated with steroids, cyclosporine-A, oxymetholone and ferrous sulfate prior to BMT. One patient had undergone splenectomy prior to BMT. All patients were heavily transfused prior to being referred for transplantation. They all had severe bone marrow insufficiency.

Conditioning consisted of Fludarabine (Flu) 30mg/m2 (day -5 to day -2), cyclophosphamide (cy) 15mg/kg/day (day-5 to day -2) in. The first five patients. In the subsequent 5 patients we used cy only, at same dose and schedule, as our institution started participation in a multicenter clinical trial. GVHD prophylaxis consisted of CSA 5mg/kg/day orally for one year and MMF 45mg/kg/day for 6 months.

The donors received G-CSF 5 μg/kg/d SC for 5 days before bone marrow harvest (day –4 to day 0).

Median CD34+, CD3+ and CD8+ cell count was respectively 3.5×10⁶ cells/ kg (3.5-7.0), 31×10⁶ cells/kg (30-45) and 12×10⁶ cells/kg (10-18).

All patients received G-CSF 10 micrograms/kg/day SC from day +1 until neutrophil engraftment. Patients received filtered and irradiated blood product transfusions if needed. Antimicrobial prophylaxis consisted of trimethoprim- sulfamethoxazole, acyclovir, antibacterial and antifungal as indicated. CMV-antigenemia was performed twice weekly until day +120. All patients had complete chimerism by VNTR on day +30.

Neutropenia (≤ 500 cells/mm3) was shortly observed in 8 out of 10 pts (80%), median 4 days (2-8 d). Thrombocytopenia (≤ 20.000 cells/mm3) also occurred in 8 pts, median 7 days (4-12 d). There were no infectious complications. Only 6 patients received IV antibiotics or antifungal during the aplasia. All CMV-antigenemia were negative. One patient had late graft rejection 2 years after the transplant and was successfully treated with a 2^nd transplant using the same donor with TBI 300 rads, fludarabine 30 mg/m2 (day -4 to day -2) and Cy 20mg/kg/d (day -4 to day -2). Two out of 10 patients (20%) had grade ≥ 2 acute GVHD. One patient died of steroid-resistant acute GVHD and 1 patient developed extensive chronic GVHD which completely resolved after treatment. OS was 90% with median follow up of 53 months (range, 12 to 90 months). All patients who survived have an excellent quality of life.

The use of G-BMT for patients with bone marrow failure due to FA resulted in a rapid granulocyte engraftment with low rate of chronic GVHD. In addition, replacing MTX by MMF seems to reduce the incidence of mucositis and the hematological toxicity.