A Pilot Study of Busulfan, Cyclophosphamide and Etoposide Followed by Autologous Transplantation for Acute Myeloid Leukemia in Remission (2000)

Patients with acute myeloid leukemia (AML) have experienced an improvement in outcome with current intensification regimens [1]. However, some subsets of patients may have an increased likelihood of relapse. Individuals with AML who fall into this category include those without favorable cytogenetic abnormalities such as inversion 16, t(8;21) or t(15;17) [3, 4, 5], those with AML French-American-British Classification (FAB) M0, M4, M5 or M6 [6], those with a high white blood cell count (WBC) at diagnosis [7], and those expressing CD34 antigen on their blasts [8]. Moreover, patients in whom a remission is reinduced following a relapse are also at a very high risk for relapse. Some of these patients can be consolidated with allogeneic hematopoietic stem cell transplantation (HSCT). However, autologous HSCT may be the only viable option in individuals without a suitable donor or those who would be intolerant of allogeneic transplantation. We report the preliminary results of a pilot study utilizing busulfan, cyclophosphamide and etoposide (BuCEt) followed by autologous HSCT in patients with AML in first or greater complete remission (CR1 or greater).Adults aged 15 years or older with AML in CR1 or greater who did not have a suitable donor were eligible for this study. Furthermore, adults aged 40 years or older in CR1 were also eligible irrespective of donor status. Ineligibility criteria included a left-ventricular ejection fraction of <50%, a lung diffusion capacity of <50% of the predicted value, a creatinine clearance of <50 ml/min, hepatic transaminases >twice normal values, and a Karnofsky performance score of <70%. The source of hematopoietic stem cells (HSC) was either the bone marrow or the peripheral blood. Bone marrow was harvested from the posterior iliac crests under general anesthesia. Peripheral blood stems cells (PBSC) were harvested after a mobilization regimen of etoposide 60 mg/kg ideal body weight i.v. (hour 0–18), cyclophosphamide 3 g/m2 i.v. in two divided doses (hour 24–25 and 30–31), paclitaxel 200 mg/m2 i.v. (hour 48–51) (TEC), and granulocyte colony-stimulating factor (G-CSF) 5 µg/kg/day i.v. from hour 60 until recovery of the absolute neutrophil count (ANC >1 × 109/l) and collection of the PBSC. The conditioning regimen consisted of busulfan 1 mg/kg/day p.o., administered 4 times each day for 4 days (days –7, –6, –5 and –4), etoposide 60 mg/kg ideal body weight i.v. over 18 h on day –3, and cyclophosphamide 45 mg/kg i.v. over 1 h times two doses administered 6 h apart on day –2 (BuCEt). Cryopreserved HSC were thawed and infused on day 0. A Hickman-type double- or triple-lumen catheter was inserted prior to transplantation. During the transplant admission, the oral cavity-care protocol consisted of nystatin liquid one million units swish and swallow four times daily, and half strength hydrogen peroxide swish and expectorate four times daily. G-CSF 5 µg/kg/day i.v. was given from day +1 until the ANC exceeded 5 × 109/l. Ciprofloxacin 500 mg orally twice daily was administered as prophylaxis against gram-negative bacteria from the beginning of conditioning chemotherapy until engraftment or fever requiring the initiation of parenteral antibiotic therapy. Individuals who were sero-positive for Herpes simplex received prophylactic acyclovir 400 mg orally twice daily from the beginning of conditioning chemotherapy until day +50 following transplantation. Co-trimoxazole (800 mg/160 mg), orally twice daily every Monday and Thursday was administered for 3–12 months following engraftment as prophylaxis against Pneumocystis carinii pneumonia. Packed red blood cells were transfused if the hemoglobin was below 8.5 g/dl. Platelet products were transfused if the platelet count was less than 20 × 109/l. CR was defined in accordance with the National-Cancer-Institute-sponsored workshop [9]. Regimen-related toxicity was evaluated utilizing the World Health Organization and Bierman criteria [10, 11]. Leukemia-free survival (LFS) and overall survival (OS) were plotted using Kaplan-Meier estimates. Several variables were examined as potential factors for predicting LFS and OS. These included age, sex, FAB classification, cytogenetic status, CD34 status and type of CR. Contingency table (ϰ2) analyses were used to estimate the statistical significance of each discrete variable.Twenty-three consecutive individuals were eligible for this study. However, 2 patients in CR1, both of whom were aged >40 years, failed to mobilize stem cells and were deemed ineligible for the study. A third patient in CR1 was intolerant of the mobilization regimen and refused further participation in the study. Twenty patients with AML in remission (13 patients in CR1 and 7 patients in CR2 or greater) underwent autologous HSCT between March, 1993, and September, 1999. Their median age was 35 years (range 15–63 years) and the sex ratio was 9 males:11 females. The FAB subtypes were 2 M1, 3 M2, 1 M3, 5 M4 and 2 M5 among patients in CR1, and 1 M0, 1 M1, 4 M3 and 1 M4 among patients in greater than CR1. Leukemic blasts expressed the CD34 antigen in half of the patients. Nine patients demonstrated karyotypic abnormalities. Only 4 individuals (1 CR1 and 3 CR2) possessed favorable cytogenetic abnormalities. Patients in CR1 had received a median of one remission induction regimen (range 1–2) and one intensification/consolidation treatment (range 1–5). The median interval from diagnosis to transplantation among patients in CR1 was 7 months (range 4–12 months). Patients in greater than CR1 had received a median of two remission induction regimens (range 2–3) and three intensification/consolidation regimens (range 2–6) during the entire course of their disease. PBSC collection was attempted in 15 patients and was successful in yielding a median of 9.8 × 106 CD34+ cells/kg (range 3.8–47 × 106/kg) in 11 individuals. The remaining 9 patients, including those in whom an attempt at PBSC mobilization had not been successful, underwent bone marrow harvesting for a median yield of 2.4 × 108 mononuclear cells/kg (range 1–3.9 × 108/kg).The median duration of neutropenia (ANC <0.5 × 109/l) was 6 days (range 4–26 days). Engraftment (ANC >1 × 109/l) took place on a median of day +10 (range day +8 to day +28). The median numbers of packed red blood cell products and platelet products transfused were 2 (range 0–9) and 5 (range 1–23), respectively. Grades of toxicity observed with this regimen are outlined in detail in table 1. Eleven individuals developed fever while neutropenic. Bacteremia was identified in 6 of these patients consisting of Staphylococcus epidermidis (n = 4) and viridans streptococci (n = 2). Kaplan-Meier estimates of LFS and OS are 49 and 54%, respectively, at 7 years of follow-up (fig. 1a, b). There was one treatment-related mortality on day +14 secondary to sepsis and respiratory failure in a patient who underwent bone marrow transplantation in CR2. Nine other patients (7 in CR1 and 2 in CR2) relapsed at a median of 7 months (range 6 weeks to 25 months) following autologous HSCT. Eight of these 9 individuals died at a median of 2.5 months (range 1 week to 8 months) following relapse. The median follow-up of the 11 surviving patients is 45 months (range 15–85 months). Moreover, 2 of the 3 patients in CR1, who were excluded from the study because of failure to mobilize PBSC or intolerance of mobilization chemotherapy, also remain in remission. None of the variables examined as potential factors predicting LFS including age equal to or greater than median versus less than median (p = 0.371), male versus female sex (p = 0.178), FAB M2, 3, or 4 versus other types (p = 0.317), favorable or normal cytogenetic tests versus abnormal cytogenetics (p = 0.771), CD34 positivity versus CD34 negativity (p = 0.387), and CR1 versus CR2 or greater (p = 0.653) achieved statistical significance. Similarly, these variables also failed to correlate with OS.Autologous HSCT transplantation has been utilized in an effort to improve the outcome of patients with AML in CR1 [12]. Randomized studies in adult patients have demonstrated either an improvement over standard therapy [13, 14]or no significant difference [15, 16, 17]. Patients with poor prognostic features based on karyotype [3, 4, 5, 18], morphology [6]and flow cytometry [8]may be most likely to benefit from myeloablative chemotherapy and autologous transplantation, especially if an allogeneic donor is not available. Autologous transplantation can also result in prolonged LFS in 21–52% of patients with AML in CR2 or greater [12]in the absence of an allogeneic donor. We utilized a combination of TEC along with G-CSF to mobilize and harvest PBSC. This regimen was successful especially among patients with AML in CR1, likely because these individuals had received less prior chemotherapy. The transplantation regimen administered in this study was tolerated well and was associated with few adverse effects, and only one heavily pretreated patient died from sepsis in the early posttransplantation period. Patients who underwent an autologous bone marrow transplantation after a failed attempt at PBSC mobilization had a prolonged period of transfusion dependency. Only 1 patient in this study fulfilled the criteria of good-risk AML (CR1 with the t(15;17) translocation). The remaining patients were at standard or high risk for relapse. The results of this pilot trial suggest that BuCEt is easy to administer and well tolerated. Together with autologous HSCT, it can produce long-term LFS in 49% of patients at standard or high risk for relapse. This regimen appears to be effective in both CR1 as well as CR2 or greater. Further study is warranted.