Allogeneic Hematopoietic Stem Cell Transplantation for Patients with Severe Aplastic Anemia Following Nonmyeloablative Conditioning Using 200-cGy Total Body Irradiation and Fludarabine (2006)

In patients with aplastic anemia (AA), allogeneic stem cell transplantation (ASCT) is the treatment of choice for younger patients with HLA-matched siblings. In patients older than 40 years, transplant-related mortality approaches 50% and survival does not differ between patients who receive ASCT and those who receive immunosuppressive therapy [1Horowitz M.M. Current status of allogeneic bone marrow transplantation in acquired aplastic anemia.Semin Hematol. 2000; 37: 30-42Abstract Full Text PDF PubMed Scopus (94) Google Scholar]. In this age group, immunosuppressive therapy has been advocated as upfront therapy, with ASCT offered only for failed immunosuppressive therapy or relapse [2Marsh J.C. Ball S.E. Darbyshire P. et al.Guidelines for the diagnosis and management of acquired aplastic anaemia.Br J Haematol. 2003; 123: 782-801Crossref PubMed Scopus (149) Google Scholar]. However, this approach gives rise to 2 major concerns: a longer interval from diagnosis to transplantation and an increase in the number of transfusions received. Both factors have been recognized as adverse risk predictors for inferior outcomes in patients undergoing ASCT for AA. The recent introduction of less intense nonmyeloablative (NM) conditioning regimens has not only resulted in lower transplant-related mortality but also widened the age range of potential recipients suitable for transplantation and includes those who are less medically fit [3McSweeney P.A. Niederwieser D. Shizuru J.A. et al.Hematopoietic cell transplantation in older patients with hematologic malignancies replacing high-dose cytotoxic therapy with graft-versus-tumor effects.Blood. 2001; 97: 3390-3400Crossref PubMed Scopus (1237) Google Scholar]. We report our preliminary experience with the use of an NM preparative regimen for ASCT in 8 patients with severe AA. Between November 2000 and October 2005, 8 patients (median age, 43 years; age range, 25-48 years) with acquired, very severe AA (n = 4) or severe AA (n = 4) were enrolled in a treatment protocol that was approved by the ethics committee of Singapore General Hospital. Written informed consent was obtained in all cases. Patient and treatment characteristics are listed in Table 1.Table 1Baseline Characteristics, Grafts, and GVHD Prophylaxis of 8 Patients with AA⁎NA indicates data not available; F, female; M, male; D, donor; R, recipient; HSCT, hematopoietic stem cell transplant; SAA, severe aplastic anemia; vSAA, very severe aplastic anemia; PNH, paroxysmal nocturnal hemogloblinuria; MNC, mononuclear cells; GVHD, graft–versus-host disease; CSP, cyclosporine; MMF, mycophenolate mofetil; MTX, methotrexate; CMV, cytomegalovirus; GCSF, granulocyte colony-stimulating factor; ATG, antithymocyte globulin.Patient No.DiagnosisDonorD/R Age (y)D/R GenderTime from Diagnosis to HSCT (mo)Prior TherapyCD34 Dose Infused (×106/kg)MNC Dose Infused (×108/kg)GVHD ProphylaxisD/R CMV Status1SAAMatched sibling49/48M/F2No6.5616.14CSP/MMF+/+2SAAMatched sibling34/47M/F60ATG/CSP3.3434.37CSP/MMF+/+3SAAMatched sibling42/46F/M6ATG/CSP11.468.24CSP/MMF/MTX−/−4vSAAMatched sibling27/35F/M3No5.278.79CSP/MMF/MTX−/+5vSAAMatched unrelated25/43M/F6CSP, GCSF, erythropoietin, oxymetholone5.99.08CSP/MMF/MTX−/−6vSAAMatched sibling55/46M/F2No6.6520.25CSP/MMF/MTX−/+7vSAAMatched sibling27/25F/M1No22.896.40CSP/MMF/MTXNA8PNH with SAAMatched sibling24/26F/F3No7.3013.33CSP/MMF/MTX+/+ NA indicates data not available; F, female; M, male; D, donor; R, recipient; HSCT, hematopoietic stem cell transplant; SAA, severe aplastic anemia; vSAA, very severe aplastic anemia; PNH, paroxysmal nocturnal hemogloblinuria; MNC, mononuclear cells; GVHD, graft–versus-host disease; CSP, cyclosporine; MMF, mycophenolate mofetil; MTX, methotrexate; CMV, cytomegalovirus; GCSF, granulocyte colony-stimulating factor; ATG, antithymocyte globulin. Open table in a new tab Unmanipulated filgrastim-mobilized peripheral blood stem cells at a median cell dose of 6.56 × 106/kg CD34+ cells (range, 3.34-22.89 × 106/kg) were infused into recipients after a conditioning regimen that was adapted from McSweeney et al [3McSweeney P.A. Niederwieser D. Shizuru J.A. et al.Hematopoietic cell transplantation in older patients with hematologic malignancies replacing high-dose cytotoxic therapy with graft-versus-tumor effects.Blood. 2001; 97: 3390-3400Crossref PubMed Scopus (1237) Google Scholar], which consisted of fludarabine 30 mg/m2 (days −4 to −2) and total body irradiation 2 Gy (day 0). Acute graft-versus-host disease (GVHD) prophylaxis consisted of cyclosporine 6.25 mg/kg twice daily from day −3 to day +100, followed by a taper until day +180; mycophenolate mofetil 15 mg/kg twice daily from day 0 to day +50, with a subsequent taper to day 100; and a short course of intravenous methotrexate (MTX; 15 mg/m2 on day +1, 10 mg/m2 on days +3, +6, and +11) for all but the first 2 patients (patients 1 and 2), who were given only cyclosporine and mycophenolate mofetil. The conditioning regimen was well tolerated in all patients, with no grade 3 or 4 regimen-related mucositis, nausea, vomiting, diarrhea, veno-occlusive disease of the liver, hemorrhagic cystitis, or cardiac or pulmonary toxicity seen (National Cancer Institute common toxicity criteria) [4Common terminology criteria for adverse events. Available at: http://ctep.cancer.gov/reporting/ctc.htmlGoogle Scholar]. All patients achieved prompt and sustained engraftment (Table 2). Median time to a neutrophil count >.5 × 109/L was 18 days (range, 13-21 days), and median time to an unsupported platelet count >20 × 109/L was 13 days (range, 8-25 days). Red blood cell and platelet transfusion independence were achieved in evaluable patients at medians of 8 days (range, 1-17 days) and 10 days (range, 6-20 days), respectively. Chimerism analysis on day +28 showed mixed chimerism (87.5%-95%) in all patients. This mixed chimerism persisted at 3-6 months after transplantation in 6 surviving patients, with 4 of these patients achieving full donor chimerism by 6-12 months. No secondary graft failure was seen.Table 2Clinical Outcome of 8 Patients with AA Undergoing NM Transplantation⁎aGVHD indicates acute graft-versus-host disease; cGVHD, chronic graft-versus-host disease; CMV, cytomegalovirus.Patient No.Days to Neutrophil Count >0.5 × 109/LDays to Platelet Count >20 × 109/LInfective Complications Within 100 DaysaGVHD Grade/SitecGVHDCurrent StatusCause of DeathFinal Chimerism Studies1Never†Neutrophil count never decreases to <.5 × 109/L.12Fungal pneumonia3/liver—Dead, day 70Invasive fungal infection100% on day 562Never†Neutrophil count never decreases to <.5 × 109/L.15Disseminated fungal infections3/liver—Dead, day 64Invasive fungal infection100% on day 5631613No1/gutNoAlive, day 1546—100% at 3 y41919CMV antigenemiaNoLimited/skinAlive, day 1343—100% at 3 y51513NoNoLimited/skinAlive, day 753—100% at 2 y61612CMV antigenemiaNoNoAlive, day 657—100% at 18 mo72121CMV antigenemia2/gutExtensive/oral/skinAlive, day 516—100% at 15 mo82112NoNoNE‡Not evaluable for cGVHD.Alive, day 132—87.5% at 3 mo aGVHD indicates acute graft-versus-host disease; cGVHD, chronic graft-versus-host disease; CMV, cytomegalovirus.† Neutrophil count never decreases to <.5 × 109/L.‡ Not evaluable for cGVHD. Open table in a new tab Grade 2-4 acute GVHD was observed in 3 patients (2 with grade 3 and 1 with grade 2). The 2 patients (patients 1 and 2) who did not receive MTX as GVHD prophylaxis developed grade 3 acute GVHD, leading to subsequent invasive fungal infections and death. Chronic GVHD was observed in 3 patients (2 with limited and 1 with extensive GVHD), including 1 patient who received an allograft from a matched unrelated donor, and all responded to calcineurin inhibitors. With a median follow-up of 24 months (range, 4-52 months), all 6 patients who received MTX-containing GVHD prophylaxis are alive, are independent of transfusion, and have Karnofsky performance scores >90%. Four of the matched sibling recipients and 1 unrelated donor allograft recipient maintained full donor chimerism during the final follow-up. One patient (patient 8) with paroxysmal nocturnal hemoglobinuria had sustained engraftment with mixed chimerism (87.5% donor chimerism) and no detectable paroxysmal nocturnal hemoglobinuria clone by fluorescence-activated cell sorting determination of CD55 and CD59 at 4 months’ follow-up. The feasibility of ASCT using an NM preparative regimen in AA remains to be established, mainly due to concerns of a high risk of graft rejection, in particular among patients who receive multiple transfusions. The results seen in this small cohort of patients have highlighted several important points. (1) This minimal conditioning regimen was sufficiently immunosuppressive in allowing prompt and stable engraftment among patients with AA. (2) It was associated with minimal toxicity, with no patients developing early grade ≥3 regimen-related toxicity, which had been seen in patients after conditioning with cyclophosphamide and antithymocyte globulin [5Storb R. Blume K.G. O’Donnell M.R. et al.Cyclophosphamide and antithymocyte globulin to condition patients with aplastic anemia for allogeneic marrow transplantations the experience in four centers.Biol Blood Marrow Transplant. 2001; 7: 39-44Abstract Full Text Full Text PDF PubMed Scopus (139) Google Scholar]. This is potentially beneficial in allowing transplantation to be performed in the outpatient setting. (3) This approach also avoids the use of T-cell–depleting agents such as antithymocyte globulin or alemtuzumab. Omission of these T-cell–depleting agents may have resulted in a more rapid post-transplantation immune reconstitution and reduction of infections such as cytomegalovirus (CMV). Three of 8 patients developed CMV antigenemia with no observed CMV disease. This finding compares favorably with other alemtuzumab- or antithymocyte globulin–based NM transplant series, which reported CMV infection rates that exceeded 50% [6Mohty M. Faucher C. Vey N. et al.High rate of secondary viral and bacterial infections in patients undergoing allogeneic bone marrow mini-transplantation.Bone Marrow Transplant. 2000; 26: 251-255Crossref PubMed Scopus (112) Google Scholar, 7Chakrabarti S. Mackinnon S. Chopra R. et al.High incidence of cytomegalovirus infection after nonmyeloablative stem cell transplantation potential role of Campath-1H in delaying immune reconstitution.Blood. 2002; 99: 4357-4363Crossref PubMed Scopus (340) Google Scholar]. (4) Addition of MTX into the GVHD prophylaxis regimen could account for the more favorable outcome, with no fatal GVHD seen among the 6 patients who received the MTX-containing GVHD prophylaxis. (5) Five of the 8 patients (63%) in this series were >40 years old at the time of transplantation, and 3 of these patients remained disease free and alive at >20 months’ follow-up. These encouraging results provide a rationale for conducting larger studies with this less intensive conditioning regimen as upfront therapy in older patients or patients who have comorbidities precluding high-dose cyclophosphamide conditioning. The uniform and durable engraftment in the current 8 multiply transfused patients is encouraging. This is partly attributed to the use of peripheral blood stem cells that contained a higher CD34+ cell dose and approximately 10-fold the number of T cells. However, reservations remain with the use of peripheral blood stem cells because of the increased risk of chronic GVHD, although a recent report has quoted a low incidence of 26% chronic GVHD when using similar approach in patients with AA [8Gomez-Almaguer D. Vela-Ojeda J. Jaime-Perez J.C. et al.Allografting in patients with severe, refractory aplastic anemia using peripheral blood stem cells and a fludarabine-based conditioning regimen the Mexican experience.Am J Hematol. 2006; 81: 157-161Crossref PubMed Scopus (38) Google Scholar]. Clearly, improved GVHD control remains a critical future research objective. Optimizing immunosuppression by prolonging cyclosporine therapy and dose-adapted mycophenolate mofetil might be a promising way to decrease GVHD [9Kliem C. Hegenbart U. Maris M. et al.Low dose mycophenolate mofetil (MMF) draft serum levels correlate with the occurrence of acute GVHD grade II-IV after allogeneic hematopoietic stem cell transplantation (HSCT) following low dose TBI with/ without fludarabine and immunosuppression with CyA/MMF.Bone Marrow Transplant. 2002; 29 (Abstract P588.): S148Google Scholar]. In conclusion, our results suggest that ASCT using an NM conditioning regimen results in stable engraftment and favorable outcome in patients with AA, including patients who are >40 years old and those who receive unrelated allografts. These promising results, although based on a small number of patients, merit further investigation and confirmation on a larger cohort of patients with longer follow-up.