Allogeneic hematopoietic cell transplantation for myelofibrosis: A 10‐year experience at single institution
Authors: Taiga Nishihori, Janelle Perkins, Jongphil Kim, Teresa Field, Joseph Pidala, Jaime Roman‐Diaz, Rami S. Komrokji, Hugo F. Fernandez, Claudio Anasetti, Mohamed A. Kharfan‐Dabaja
Journal: American Journal of Hematology (2010)

Allogeneic hematopoietic cell transplantation (HCT) remains the only curative approach for patients with myelofibrosis [1, 2]; however, it can result in substantial transplant related mortality. We retrospectively examined the outcomes of 18 myelofibrosis patients who underwent allogeneic HCT between 2000 and 2008. Eleven (61%) had high-risk prognostic scores. Fourteen (78%) received a reduced-toxicity regimen of pharmacokinetically-targeted (a median AUC of 5,300 μm min−1; range, 3,500–6,000) intravenous busulfan plus fludarabine (t-IV Bu/Flu). Source of hematopoietic cells were from HLA matched-related (50%), matched-unrelated (44%), or mismatched-unrelated (6%) donors. Fourteen (78%) received G-CSF-mobilized peripheral blood stem cells. Median time to neutrophil and platelet engraftment were 17 (range, 15–28) and 18 (range, 8–213) days, respectively. There were two cases of secondary graft failure after myeloablative conditioning and one case following t-IV Bu/Flu. Overall survival was 50.2% at 54 months (95% confidence interval [C: 24.1–71.6%) with a median follow-up of 15 (range, 3–63) months. Nonrelapsed mortality (NRM) at 100 days and at 1-year were 0 and 22.6% (95% CI: 9.1–49.7%), respectively. The causes of NRM comprised of infections (56%) and graft-versus-host-disease (44%). t-IV Bu/Flu is a feasible conditioning regimen for allogeneic HCT in myelofibrosis showing encouraging engraftment with 7% graft failure rate. Myelofibrosis is a clonal hematopoietic disorder characterized by bone marrow fibrosis, leukoerythroblastic features, splenomegaly, constitutional symptoms, and extramedullary hematopoiesis [3-5]. The Lille scoring system is a prognostic model that helps stratify patients with myelofibrosis [6]. Intermediate-risk group (1 factor) and high-risk group (2 factors) have a median survival of 26 months and 13 months, respectively. Allogeneic HCT is a potentially curative treatment option for patients with primary myelofibrosis or myelofibrosis secondary to polycythemia vera (PV) or essential thrombocythemia (ET) [1, 2]. Wider applicability of allogeneic HCT had been limited by the significant risks of transplant-related mortality resulting from myeloablative conditioning regimens, especially in the older patient population [7-10]. Reduced toxicity regimens have been used to facilitate allogeneic HCT in older myelofibrosis patients with encouraging results [11-16]. A combination of intravenous busulfan and fludarabine (IV Bu/Flu) has been demonstrated safe and effective as conditioning regimen in myeloid malignancies [17-19]. Pharmacokinetic analysis has been performed with IV busulfan administration, however, no large-scale trials have been undertaken to examine the safety and efficacy of t-IV Bu/Flu, specifically in myelofibrosis. Eighteen patients received allogeneic HCT for myelofibrosis between 2000 and 2008 at Moffitt Cancer Center. The baseline characteristics of these patients are listed in Table I. There were 10 (56%) men and 8 (44%) women. The Lille and International Prognostic Scoring System for myelofibrosis (IPSS-MF) scores were calculated at the time of transplant [6, 20]. Three (17%) patients had constitutional symptoms. Therapy received prior to allogeneic HCT is shown in Table II. Seventeen patients had bone marrow fibrosis information available pre-transplant and all had increased reticulin fibers. Five patients had osteosclerosis. Median time to neutrophil and platelet engraftment was 17 (range, 15–28) days and 18 (range, 8–213) days, respectively. All patients engrafted neutrophils initially. All but one patient conditioned with t-IV Bu/Flu achieved platelet engraftment within 30 days. One patient had pre-transplant platelet count of over 1,000,000 μL and platelet count nadir was at 40,000 μL. There were three cases of delayed platelet engraftment (> 30 days). One patient who was conditioned with busulfan and cyclophosphamide (Bu/Cy) experienced both delayed WBC (day +28) and platelet (day +213) engraftment. Three patients experienced secondary graft failure: one patient with fludarabine and melphalan (Flu/Mel) conditioning received second infusion of cells on day +89 due to secondary graft failure, another patient conditioned with cyclophosphamide with total body irradiation (Cy/TBI) developed secondary graft failure at 3 months, and a third patient who received t-IV Bu/Flu developed secondary graft failure at 11 months. Median donor bone marrow (BM) chimerism (unsorted) was 97.5% (range, 91–100: n = 14) on day +30, 99.5% (range, 92–100: n = 12) on day +90, and 100% (range, 67–100: n = 10) on day +180. Median CD3+ peripheral blood (PB) chimerisms were 58.5% (range, 44–100) on day +30, 64.5% (range, 45–100) on day +90, and 83.5% (range, 37–100) on day +180. Median CD33+ PB chimerisms were 100% (range, 100–100) on day +30, 100% (range, 100–100) on day +90, and 100% (range, 45–100) on day +180. Fourteen (74%) patients developed Grade II–IV acute graft-versus-host disease (GVHD). Maximum acute GVHD overall grades were: Grade I = 3 (17%), Grade II = 8 (44%), and Grade III = 6 (39%). There was no Grade IV acute GVHD. Fourteen (78%) patients developed chronic GVHD (limited = 8, extensive = 6). Overall, marrow fibrosis improved or resolved in 13 (76%) of 17 cases. Three patients had stable marrow fibrosis and there were no relapses of marrow fibrosis. One patient did not have assessment on the degree of marrow fibrosis post-allograft. Splenomegaly improved in 7 (54%) of 13 patients. There were three patients with JAK2V617F mutation and all became negative post-transplantation. Overall survival (OS) by Kaplan–Meier method is 50.2% at 54 months (95% CI: 24.1–71.6%) with a median follow-up of 15 (range, 3–63) months, as shown in the Figure 1A. There was a trend toward improved probability of survival in patients with intermediate Lille risk group compared to high Lille risk group (P = 0.124 by Log Rank test; Fig. 1B). There was no association with IPSS-MF (not shown). NRM at 100 days and at 12 months were 0 and 22.6% (95% CI: 9.1–49.7%), respectively (Fig. 1C). The causes of NRM comprised of infections (n = 5, 56%) and GVHD (n = 4, 44%). OS curve of 14 patients who received t-IV Bu/Flu conditioning regimen is shown in Fig. 1D. One patient progressed to acute myeloid leukemia 1-year posttransplant and later received second matched unrelated donor hematopoietic cell transplant. However, the patient developed steroid-refractory GVHD with multi-organ failure and expired on day +51 after second transplant. Overall survival after allogeneic stem cell transplantation (Panel A). Impact of Lille risk category on survival (Panel B). Cumulative incidence of nonrelapse mortality (Panel C). Overall survival curves based on conditioning regimens (Panel D). One patient conditioned with Cy/TBI developed idiopathic pneumonia syndrome (IPS) on day +23 post transplant requiring high-dose methylprednisolone. The patient required supplemental oxygen but no ventilator support and ultimately recovered from IPS. Another patient who was conditioned with Bu/Cy developed diffuse alveolar hemorrhage (DAH) on day +30 requiring high-dose steroid treatment with subsequent improvement. None of the patients treated with t-IV Bu/Flu experienced significant toxicities including seizure, hepatic sinusoidal obstruction syndrome/veno-occlusive disease (SOS/VOD) or IPS related to busulfan. Overall toxicities observed in all patients included Grade 2 and 3 mucositis in 7 (39%) and 11 patients (61%), respectively. Two patients (11%) developed Grade 2 renal failure which was reversible. There was one case of Grade 3 cyclophosphamide-induced hemorrhagic cystitis. In summary, we describe a single center experience of patients with myelofibrosis who underwent allogeneic HCT with mostly t-IV Bu/Flu regimen. Although limited by the heterogeneity and size of the dataset, this series demonstrates a relatively low graft failure rate in patients with myelofibrosis. This study shows a trend toward increased probability of survival after allogeneic HCT in patients with intermediate Lille risk group compared to those with high risk. The International Working Group for Myelofibrosis Research and Treatment (IWG-MRT) developed a new prognostic scoring system for myelofibrosis, IPSS-MF, which would facilitate therapeutic decision making for patients with myelofibrosis [20]. It was proposed that it would be reasonable to consider allogeneic HCT in patients with intermediate-2 risk category or higher, however, this remains to be validated in a prospective setting and our dataset did not show significant survival associations with IPSS-MF risk categories likely due to small sample size (data not shown). Reduced toxicity regimens were introduced for patients with myelofibrosis due to low regimen-related morbidity, mortality, applicability to older patients and to those with significant comorbidities. The successful application of such regimens in patients with myelofibrosis were first reported by Hessling et al. [21] and Devine et al. [13]. These preliminary reports suggested that the conditioning regimen was well tolerated and offers effective therapy. The first retrospective analysis of 21 patients with a median age of 54 years, who received various reduced toxicity regimens with matched related donors showed the NRM at 1 year of 10% and the OS at 2.5 years of 85% [11]. Similarly, a prospective study of 21 patients, with a median age of 53 years, who received a conditioning regimen of Bu/Flu and anti-thymocyte globulin (ATG) demonstrated the NRM at 1 year of 16% and OS of 84% at 3 years [12]. The experience was later extended to unrelated donors [12, 16, 22]. Overall, the most commonly used regimens were Bu/Flu or Flu/Mel based. The median age of patients was, in general, a decade older than those with myeloablative conditioning. The NRM was less than 20%, and the OS was 55–85% range [11-13, 21, 23]. Our result is comparable in terms of OS; however, it showed considerably higher rates of GVHD and NRM. This may, in part, be explained due to use of unrelated donor sources in half of the cases, high Lille risk scores in the majority and extensive prior treatment history, among others. IV Bu/Flu regimen has been previously demonstrated safe and effective in myeloid malignancies [17-19], although, pharmacokinetic targeted IV Bu/Flu has not been investigated in large scale randomized studies. Other reported reduced toxicity regimens for patients with myelofibrosis include a combination of low dose busulfan, fludarabine, and ATG [12, 14, 21-23], as well as Bu/Flu [24]. Recently, the European Group for Blood and Marrow Transplantation (EBMT) reported a prospective multicenter Phase II trial on a busulfan (10 mg kg−1)/fludarabine (180 mg m−2)-based reduced toxicity regimen in 103 patients with myelofibrosis [15]. The estimated 5-year event-free survival and OS was 51 and 67%, respectively. None of the studies have incorporated consistent pharmacokinetic targeting of busulfan dosing. Our result underscores the feasibility of t-IV Bu/Flu in older patients with myelofibrosis with low morbidity. Pharmacokinetically targeted IV Bu/Flu is a viable option for both related and unrelated donor allografting. Engraftment kinetics is encouraging despite the presence of splenomegaly and myelofibrosis. The regimen has a potential for application to a broader patient population. Eighteen patients were treated with allogeneic HCT for myelofibrosis between February 25, 2000 and December 19, 2008 at Moffitt Cancer Center. The analysis was performed in March 2010. Restaging for myelofibrosis occurred at days +30, +90, +180, +360, and yearly thereafter posttransplant. All patients signed inform consents for a long-term follow-up study of their transplant outcomes, approved by the University of South Florida (USF) Institutional Review Board (IRB). The present retrospective review of patient outcomes was also approved by the USF IRB. Fourteen patients received with t-IV Bu/Flu consisting of fludarabine 40 mg m−2 IV infused over 30 min on days -6 to -3, followed by IV busulfan 130–170 mg m−2 over 3 hr daily on the same days. Busulfan pharmacokinetic samples were obtained on day -6 and analyzed by gas chromatography/mass spectrometry by the University of Pennsylvania clinical toxicology laboratory; the busulfan dose was adjusted for the remaining two doses (on days -4 and -3) to target a median AUC of 5300 (±10%) μm min−1 (range, 3,500–6,000 μm min−1) for each of the 4 days. Antithymocyte globulin (ATG) was administered to one patient with HLA-B mismatched allograft with t-IV Bu/Flu. One other patient received fludarabine 40 mg m−2 per day × 4 days and melphalan 70 mg m−2 per day × 2 days. Other regimens included busulfan 0.8–1.0 mg kg−1 orally every 6 hr for 16 doses and cyclophosphamide 60 mg kg−1 day−1 IV × 2 days (two patients), and cyclophosphamide 60 mg kg−1 day−1 IV × 2 days and total body irradiation (1,320 cGy in 11 fractions) (one patient). GVHD prophylaxis consisted of tacrolimus and methotrexate (n = 11), tacrolimus plus mycophenolate mofetil (n = 4), and a cyclosporine-based regimen (n = 3). All patients except one were evaluated for chimerism at days +30, +90, +180, and +360 after transplantation by polymerase chain reaction (PCR). The sources of material included unsorted BM and PB. In 14 patients (78%), STR-PCR analyses were also performed on cell subsets with CD3 and CD33 positivity. One patient who received Cy/TBI was evaluated for chimerism by fluorescence in situ hybridization (FISH) only on BM. Neutrophil engraftment is defined by the first of three successive days with an absolute neutrophil count (ANC) > 500 μL. Platelet engraftment is defined by the first of three successive days with a nontransfused platelet count >20,000 μL. Primary graft failure is defined as failure to achieve an ANC of 500 μL within 28 days following transplantation for patients who have not undergone a second transplant procedure. Secondary graft failure is defined as decline of an ANC <500 μL after having engrafted that is unresponsive to growth factors and unrelated to effects of medications or infection. Acute GHVD (aGVHD) was scored per modified Glucksberg criteria within 100 days from transplant [25]. Chronic GVHD (cGVHD) was staged per previous standard criteria [26, 27]. OS was estimated from date of transplantation using the Kaplan–Meier method [28]. Survival curves stratified by Lille score and donor relation were compared using the log-rank test. Since there was no relapsed patient, nonrelapse mortality (NRM) is equal to 1 – OS. The authors thank Ms. Diane Coyle for her valuable work on data management. Taiga Nishihori [email protected]* , Janelle Perkins* , Jongphil Kim , Teresa Field* , Joseph Pidala* , Jaime Roman-Diaz*, Rami S. Komrokji §, Hugo F. Fernandez* , Claudio Anasetti* , Mohamed A. Kharfan-Dabaja* , * Department of Blood and Marrow Transplantation, H. Lee Moffitt Cancer Center and Research Institute, University of South Florida, Tampa, Florida, Department of Oncological Sciences, University of South Florida, Tampa, Florida, Department of Biostatistics, H. Lee Moffitt Cancer Center and Research Institute, University of South Florida, Tampa, Florida, § Department of Hematologic Malignancies, H. Lee Moffitt Cancer Center and Research Institute, Tampa, Florida.