Mycobacterium chelonae necrotizing pneumonia after allogeneic hematopoietic stem cell transplant: report of clinical response to treatment with tigecycline

We present a case of progressive Mycobacterium chelonae ssp. chelonae necrotizing pneumonia after hematopoietic stem cell transplantation (HSCT) in the presence of chronic graft-versus-host disease. The patient failed to respond to standard combination therapy with multiple agents and developed resistance to most drugs over the course of treatment. Tigecycline, a new glycylcycline antimicrobial agent with in vitro activity against M. chelonae, was then used with a clinical response to treatment. To our knowledge, this is the first reported case demonstrating tigecycline to have a degree of clinical effectiveness to treat refractory pulmonary infection with M. chelonae in an HSCT recipient.

Low-dose cidofovir treatment of BK virus-associated hemorrhagic cystitis in recipients of hematopoietic stem cell transplant

In recipients of hematopoietic stem cell transplants (HSCTs), BK virus (BKV) has been associated with late-onset hemorrhagic cystitis (HC). In our institution, HSCT recipients with BKV-associated HC are treated with 1 mg/kg of cidofovir weekly. We identified HSCT recipients with BKV-associated HC, treated with weekly cidofovir. Microbiological response was defined as at least a one log reduction in urinary BKV viral load; clinical response was defined as improvement in symptoms and stability or reduction in the grade of cystitis. Nineteen allogeneic HSCT patients received a mean of 4.5 weekly doses of cidofovir. HC occurred at a mean of 68.7 days after transplant. A clinical response was detected in 16/19 (84%) patients, and 9/19 (47%) had a measurable microbiological response (8/10 nonresponders had a BKV viral load above the upper limit of the assay before treatment). Fourteen out of nineteen (74%) patients had no significant increase in serum creatinine. Five patients with renal dysfunction resolved after completion of the therapy and removal of other nephrotoxic agents. We conclude that weekly low-dose cidofovir appears to be a safe treatment option for BKV-associated HC. Although the efficacy of low-dose cidofovir is not proven, a prospective trial is warranted.

Lower incidence of Bronchiolitis obliterans in allogeneic hematopoietic stem cell transplantation with reduced-intensity conditioning compared with myeloablative conditioning

Bronchiolitis obliterans (BO) is one of the most devastating complications after allogeneic stem cell transplantation (HSCT). However, its true pathogenesis is still to be elucidated. We conducted this study to find whether tissue damage due to high-dose chemo-radiotherapy is related to its pathogenesis. In all, 144 patients who received allogeneic HSCT between May 1999 and October 2001, and survived more than 80 days after transplant, were analyzed. Clinical course, pulmonary function tests, imaging studies including CT scan, and pathology results were reviewed. The overall incidence of BO was 9.7% (14/144). The cumulative incidence of BO at 2 years after transplant was 17% with myeloablative conditioning, and 2.3% with reduced intensity conditioning (P=0.024). Multivariate analysis showed that myeloablative conditioning was the only factor which affected the incidence of BO. Development of BO did not significantly affect the overall survival of patients. However, if they developed BO earlier than 200 days post transplant, the prognosis was significantly worse than if they developed it later than 200 days post transplant (P=0.003) or if they did not develop BO (P=0.002). Our results imply that tissue damage secondary to intensive chemo-radiotherapy may contribute to the pathogenesis of BO.

Reduced-intensity allogeneic hematopoietic stem cell transplantation for acute leukemias: ‘what is the best recipe?’

Reduced-intensity stem cell transplantation (RIST) has been shown to be a safe and useful alternative transplant method for patients including elderly and medically unfit patients. RIST conditioning regimens vary widely in the intensity of myeloablation, immunoablation, and antileukemia effects, and thus optimal regimen for each disease entity is yet to be determined. Most reports on RIST to date are small, single-institution experiences or retrospective studies with heterogeneous patient populations and primary diseases, complicating any direct comparison between studies. In acute myeloid leukemia (AML), moderate-intensity regimens may be effective, achieving 30-70% 1-year disease-free survival in various series, but minimal-intensity regimens are associated with high relapse rates. In acute lymphoblastic leukemia (ALL), not even moderate-intensity regimens are effective and most patients with advanced ALL relapse post transplant. Thus, the risk/benefit ratios of graft-versus-host disease/graft-versus-leukemia effect differ among diseases. Larger, prospective, multi-center clinical trials are needed to determine the best use of RIST in hematologic malignancies.

Pegfilgrastim after high-dose chemotherapy and autologous peripheral blood stem cell transplant: phase II study

Pegfilgrastim is equivalent to daily filgrastim after standard dose chemotherapy in decreasing the duration of neutropenia. Daily filgrastim started within 1-4 days after autologous stem cell transplant (ASCT) leads to significant decrease in time to neutrophil engraftment. We undertook a study of pegfilgrastim after high-dose chemotherapy (HDC) and ASCT. In all, 38 patients with multiple myeloma or lymphoma, eligible to undergo HDC and ASCT, were enrolled. Patients received a single dose of 6 mg pegfilgrastim subcutaneously 24 h after ASCT. There were no adverse events secondary to pegfilgrastim. All patients engrafted neutrophils and platelets with a median of 10 and 18 days, respectively. The incidence of febrile neutropenia was 49% (18/37). Neutrophil engraftment results were compared to a historical cohort of patients who received no growth factors or prophylactic filgrastim after ASCT. Time to neutrophil engraftment using pegfilgrastim was comparable to daily filgrastim and was shorter than in a historical group receiving no filgrastim (10 vs 13.7 days, P<0.001). Pegfilgrastim given as a single fixed dose of 6 mg appears to be safe after HDC and ASCT. It accelerates neutrophil engraftment comparable to daily filgrastim after ASCT. Pegfilgrastim may be convenient to use in outpatient transplant units.

Clinical significance of cytomegalovirus (CMV) antigenemia in the prediction and diagnosis of CMV gastrointestinal disease after allogeneic hematopoietic stem cell transplantation

To evaluate the clinical significance of a cytomegalovirus (CMV) antigenemia assay in the prediction and diagnosis of CMV gastrointestinal (CMV-GI) disease after hematopoietic stem cell transplantation (HSCT), 19 allogeneic HSCT recipients developing CMV-GI disease were retrospectively reviewed. All patients were monitored by a CMV antigenemia assay, at least once weekly after engraftment. The median onset of CMV-GI disease occurred 31 days post transplant (range: 19-62). Only four of 19 patients (21%) developed a positive CMV antigenemia test before developing CMV-GI diseases. Although all 19 patients subsequently developed positive CMV antigenemia tests during their clinical courses, the values remained at a low-level in nine (47%) patients. Among the 14 patients in whom results of real-time polymerase chain reaction (PCR) were available, seven (50%) yielded positive results of real-time PCR before developing CMV-GI disease. In contrast to the values of CMV antigenemia, all 14 patients exclusively yielded high viral loads (median: 2.8 x 10(4) copies/ml plasma). We conclude that CMV antigenemia testing has limited value in prediction or early diagnosis of CMV-GI disease, and that real-time PCR could have a more diagnostic significance.

Clinical impact of graft-versus-host disease against leukemias not in remission at the time of allogeneic hematopoietic stem cell transplantation from related donors. The Japan Society for Hematopoietic Cell Transplantation Working Party

Acute graft-versus-host disease (GVHD) increases post-transplant mortality and morbidity, but exerts a potent graft-versus-leukemia (GVL) effect. To clarify the impact of GVHD on outcome after transplant in aggressive diseases, patients with acute myeloid or lymphoblastic leukemia (AML, n = 366 or ALL, n = 255) in nonremission states, or chronic myelogenous leukemia (CML, n = 180) in accelerated phase (AP) or blastic crisis (BC), who received allogeneic hematopoietic stem cell transplantation (HSCT) from a related donor between 1991 and 2000, were analyzed. Significant improvement in overall and disease-free survival (DFS) was detected with grade I acute GVHD in AML (P = 0.0002 for overall survival and 0.0009 for DFS, respectively) and in CML (P = 0.0256 and 0.0366, respectively), while the trend towards improved survival was observed in ALL. Relapse rate was lower in grade I acute GVHD than in grade II in all three diseases, suggesting that treatment for grade II GVHD may compromise the GVL effect associated with GVHD. Chronic GVHD was found to suppress relapse in CML and ALL, but not in AML, although no improvement in survival was observed in any disease category. Our results suggest that treatment for grade II acute GVHD may need to be attenuated in transplant for refractory leukemias.

Allogeneic peripheral blood stem cell transplantation from two- or three-loci-mismatched related donors in adult Japanese patients with high-risk hematologic malignancies

With the increasing frequency of haploidentical transplantation, it is becoming more important to establish the degree of HLA mismatch that can be accepted. We retrospectively analyzed clinical data of 50 adult Japanese patients with high-risk hematologic malignancies who underwent allogeneic peripheral blood stem cell transplantation (PBSCT) from two- or three-loci-mismatched related donors with HLA class I and II gene disparities in the graft-versus-host direction. They were treated at 20 transplant centers between 1996 and 2002. In all, 18 patients received unmanipulated PBSC, while 32 received purified CD34+ blood cells. Conventional (n=31) or reduced-intensity (n=19) conditioning regimens were used. Of the 39 patients (78%) who survived for > or =28 days after transplant, 37 (95%) achieved neutrophil engraftment, while graft failure and rejection occurred in two of 39 (5%) and three of 37 (8%) patients, respectively. Stepwise Cox regression analysis revealed a significantly lower incidence of grades II-IV acute GVHD in patients receiving purified CD34+ cells (hazard ratio 0.32; 95% CI 0.12-0.84; P=0.022). By 1 year post transplant, 28 patients (56%) had died of transplant-related problems, including infectious complications (30%). Although the number of patients is small, our data suggest that transplant-related problems, particularly infectious complications, are major obstacles to the success of this therapy.

Immune reconstitution following reduced-intensity transplantation with cladribine, busulfan, and antithymocyte globulin: serial comparison with conventional myeloablative transplantation

The primary object of the conditioning regimen for allogeneic reduced-intensity stem cell transplantation (RIST) is immunosuppression to achieve stable engraftment of donor cells, rather than bone marrow ablation. Therefore, immune reconstitution after RIST might be different from that after conventional stem cell transplantation (CST). In this study, 22 patients underwent RIST and 28 underwent CST. The RIST regimen consisted of cladribine (2-CdA; 0.11 mg/kg/day for 6 days), BU (4 mg/kg/day for 2 days), and rabbit anti-thymocyte globulin (ATG; 2.5 mg/kg/day for 2-4 days). The CST group received either the BU (4 mg/kg/day x 4 days)/CY (60 mg/kg/day x 2 days) (n=13) or CY (60 mg/kg/day x 2 days)/TBI (4 Gy/day x 3 days) regimen (n=15). All patients underwent transplantation with G-CSF-mobilized blood stem cells. Engraftment speed after RIST was fast and seven of 22 patients did not require platelet transfusion. We noted that the numbers of CD4+, CD4+CD45RA+, and CD4+CD45RO+ T cells after transplant in the RIST group were significantly lower than those in the CST group (P=0.0001 for both the comparisons). However, the reconstitution of CD20+ B cells was faster in the RIST group (P=0.0001). The response of T cells to PHA stimulation was lower in the RIST group (P=0.0001 on day 30 and P=0.02 on day 90). Nevertheless, there were no significant differences in the incidence of bacterial, fungal, or viral infections between the two groups. We concluded that our RIST regimen might delay laboratory-evaluated T-cell immune reconstitution compared to CST; however, the observed setbacks did not directly translate into clinically significant increases in infectious episodes.

High complete response rate after allogeneic hematopoietic stem cell transplantation with reduced-intensity conditioning regimens in advanced malignant lymphoma

The possible advantage of allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a graft-versus-lymphoma effect. We explored the feasibility and efficacy of allo-HSCT with reduced-intensity (RI) regimens in advanced malignant lymphoma (ML). A total of 20 patients with indolent (n=9) or aggressive lymphoma (n=11) received allo-HSCT with an RI regimen (RIST). The preparative regimen consisted of a combination of purine analog and alkylating agent with or without antithymocyte globulin. A total of 11 patients had chemorefractory disease, seven had chemosensitive relapsed disease and two had residual disease. All of the patients received G-CSF-mobilized blood stem cells from HLA-matched siblings. Of the 20 patients, 19 achieved engraftment with acceptable regimen-related toxicities. Seven patients developed grade II-IV acute GVHD and 15 developed chronic GVHD. Of the 15 patients with evaluable disease, 12 achieved a complete response. One died of invasive fusariosis, four subsequently died of GVHD complicated with fungal infection and one died of progressive disease. With a median follow-up of 358 days, the Kaplan-Meier estimates for 1-year overall and progression-free survival were both 70%. The high response rate with low relapse observed in this study suggests that RIST may be an effective alternative curative treatment for patients with advanced ML.

Successful treatment of meningoencephalitis caused by methicillin-resistant Staphylococcus aureus with intrathecal vancomycin in an allogeneic peripheral blood stem cell transplant recipient

Methicillin-resistant Staphylococcus aureus (MRSA) is a common infectious pathogen during stem cell trans-plantation. We report a case of meningoencephalitis with multiple abscess formation caused by MRSA, which occurred in a 4-year-old boy soon after allogeneic peripheral blood stem cell transplantation. We successfully cured the infection with a combination of intravenous and intrathecal vancomycin.

Primary cutaneous aspergillosis caused by Aspergillus ustus following reduced-intensity stem cell transplantation

A 19-year-old woman with myelodysplastic syndrome underwent reduced-intensity stem cell transplantation [RIST: (cladribine 0.11 mg/kg for 6 days, busulfan 4 mg/kg for 2 days, and rabbit antithymocyte globulin)] from her one HLA-mismatched mother. Prophylaxis against graft-versus-host disease (GVHD) was performed with cyclosporine A (CSA) alone. Severe acute GVHD in the skin, gut, and liver developed concurrently with stable engraftment, and methylprednisolone was administered (1-2 mg/kg per day, then pulse therapy with 1 g/day for 3 days) until day 40 of transplant, when a necrotic lesion of 10 mm in diameter appeared on the right cheek. The initial skin biopsy of the affected area showed a nonspecific inflammatory change. Routine X-ray and computed tomography examinations of the sinuses, chest, and abdomen disclosed no particular abnormalities. Despite intensive antibiotic therapy, the lesion rapidly extended to form an ulcer. A second biopsy specimen obtained from the lesion showed massive septa hyphae, suggesting mold infection. Although we immediately started amphotericin B, she died of multiorgan failure on day 68. Postmortem DNA sequence analysis of the specimen using the polymerase chain reaction identified Aspergillus ustus. Although this is an extremely rare complication after transplantation, this case highlights that we should pay more attention to primary cutaneous aspergillosis in severely immunosuppressed patients.

Successful allogeneic blood stem cell transplantation for aplastic anemia in a patient with renal insufficiency requiring dialysis

A 27-year-old man with aplastic anemia and renal insufficiency requiring dialysis underwent allogeneic PBSCT. The preparative regimen consisted of melphalan, ATG and TLI. GVHD prophylaxis consisted of cyclosporine and prednisolone. He was dialyzed prior to administration of melphalan and at 24 and 72 h after it. Otherwise, the dialysis schedule was unchanged, at three times a week. Engraftment was rapid. Regimen-related toxicity was minimal. Pharmacokinetic parameters of melphalan were not significantly altered with its plasma half-life 1.5 h. Patients with renal failure can receive allogeneic HSCT, and a combination of melphalan, ATG and TLI may serve as an alternative to CY and ATG.

Suspected delayed immune recovery against cytomegalovirus after reduced-intensity stem cell transplantation using anti-thymocyte globulin

A reduced-intensity hematopoietic stem cell transplantation (RIST) regimen was developed to induce immunosuppression to facilitate the engraftment of donor cells. However, there have been concerns that the incidence of opportunistic infection may increase after this procedure. To address this problem, we retrospectively analyzed the medical records of 24 RIST recipients who were treated over a recent 16-month period for comparison with 31 recipients of conventional allogeneic transplantation (CST). The RIST regimen consisted of cladribine (0.66 mg/kg), busulfan (8 mg/kg), and rabbit anti-thymocyte globulin (ATG; 5-10 mg/kg). All of the patients received allogeneic peripheral blood stem cells from an HLA-identical or one-locus mismatched related donor. Although the incidence of positive CMV antigenemia was comparable between the two groups (58% vs 68%), RIST patients developed positive antigenemia significantly sooner than did CST patients (P = 0.01) and showed higher initial and maximum antigenemia values (P = 0.026 and P = 0.003, respectively). These findings may suggest that immune recovery against CMV was delayed after our RIST procedure, but this did not directly translate into an increase in clinically significant CMV disease. Early therapeutic intervention with ganciclovir might play a role in preventing the progression of early CMV infection to CMV disease.

[Non-myeloablative/reduced-intensity hematopoietic stem cell transplantation for chronic myelogenous leukemia]

Allogeneic hematopoietic stem cell transplantation(HSCT) is a curative therapy against a variety of hematological disorders. However, its application has been limited to younger patients without organ dysfunctions due to transplant-related toxicities. Recently, non-myeloablative stem cell transplantation(NST) or reduced-intensity stem cell transplantation(RIST) has been developed as a less toxic HSCT, which enables the application of HSCT to patients of advanced age or with organ dysfunction. The anti-leukemia effect mainly depends on the graft-versus-leukemia(GVL) effect. Chronic myelogenous leukemia(CML) has been known to be one of the best targets for GVL effect, supported by the observation of durable molecular remission after donor lymphocyte infusion for relapse after HSCT. RIST could be a promising treatment modality for patients with CML.

Long-term low-dose acyclovir against varicella-zoster virus reactivation after allogeneic hematopoietic stem cell transplantation

To evaluate the efficacy of long-term administration of acyclovir as prophylaxis against varicella-zoster virus (VZV) reactivation, we analyzed the medical records of 86 consecutive adult patients who obtained engraftment after allogeneic hematopoietic stem cell transplantation from January 1996 to March 2000. We started long-term low-dose (400 mg/day) oral administration of acyclovir in June 1999, and this was continued until the end of immunosuppressive therapy after transplantation. There was no breakthrough reactivation of VZV in patients receiving acyclovir. Five patients who were receiving cyclosporine or prednisolone developed VZV reactivation after discontinuing acyclovir. With this prophylaxis, the cumulative incidence of VZV reactivation at 1 year after transplantation decreased from 33% to 10% (P = 0.025). On multivariate analysis, the use of long-term acyclovir was identified as a significant independent parameter for the development of VZV reactivation. These findings suggest the efficacy of long-term prophylaxis with low-dose acyclovir. Resumption of acyclovir upon restarting immunosuppressive therapy might be important for the further prevention of VZV reactivation. The benefit of long-term low-dose acyclovir should be confirmed prospectively.

Early full donor myeloid chimerism after reduced-intensity stem cell transplantation using a combination of fludarabine and busulfan

BACKGROUND AND OBJECTIVES

The aim of this study was to evaluate lineage-specific chimerism reconstitution after reduced-intensity allogeneic stem cell transplantation (RIST) using a combination of fludarabine (30 mg/m2 for 6 days) and busulfan (4 mg/kg for 2 days).

DESIGN AND METHODS

We prospectively enrolled 8 consecutive patients with hematologic malignancies who were not candidates for conventional transplantation because of either high age or organ dysfunction. Host-donor chimerism was evaluated using polymerase chain reaction-based amplification of a polymorphic short tandem repeat region.

RESULTS

All of our patients achieved engraftment within a median of 11 days after transplantation. On day 30, full donor myeloid cell chimerism (>90%) was achieved in 7 patients whereas full donor T-cell chimerism was achieved in only one patient. Thus, in contrast to other reported results, full donor chimerism was achieved earlier in the myeloid lineage than the T-cell lineage. On day 60, however, T-cell chimerism caught up with myeloid chimerism. Two patients developed grade II-IV acute graft-versus-host disease (GVHD) before the detection of full donor T-cell chimerism.

INTERPRETATION AND CONCLUSIONS

Our findings suggest that the kinetics of lineage-specific chimerism depend on the agents used in the conditioning regimen, and may provide insight into the chimerism kinetics and pathogenesis of GVHD. Thus, the strategy for controlling immunosuppression after RIST should be modified according to the type of conditioning regimen applied.

Early onset Pneumocystis carinii pneumonia after allogeneic peripheral blood stem cell transplantation

Pneumocystis carinii (P. carinii) is one of the major opportunistic pathogens responsible for hematopoietic stem cell transplantation (HSCT)-related pneumonias. Although trimethoprim-sulfamethoxazol (TMP/SMX) prophylaxis has been shown to prevent almost all P. carinii infections, 1%-2% of patients may still experience this complication. P. carinii pneumonia (PCP) is usually a late complication in patients receiving TMP/SMX prophylaxis, with most cases occurring later than 2 months post-transplant. We report a patient who developed early onset PCP after allogeneic peripheral blood stem cell transplantation (PBSCT) from an HLA-identical sibling donor. On day 12, the patient complained of dyspnea and cough. A chest X ray showed infiltrates in right upper lobe with bilateral pleural effusion. By the findings of Grocott stain on bronchoalveolar lavage fluid obtained on day 14, he was diagnosed as having PCP. Intravenous TMP/SMX failed to improve the lesion. This is the earliest onset PCP in the literature after HSCT despite the prophylactic administration of TMP/SMX before transplant.

Successful application of nonmyeloablative transplantation for paroxysmal nocturnal hemoglobinuria

OBJECTIVE

Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired clonal hematopoietic stem cell disorder that manifests as hemolytic anemia, venous thrombosis, and deficient hematopoiesis. Although allogeneic hematopoietic stem cell transplantation is considered the only curative therapeutic measure, transplant-related mortality is not negligible. Several studies supported the use of nonmyeloablative stem cell transplantation (NST) for patients of advanced age or with organ dysfunction. Hence, we used NST in a PNH patient who suffered from acute renal failure due to repeated episodes of hemolysis.

MATERIALS AND METHODS

We performed NST using a conditioning regimen consisting of cladribine 0.11 mg/kg x 6, busulfan 4 mg/kg x 2, and rabbit anti-thymocyte globulin 2.5 mg/kg x 2. He received peripheral blood stem cells from his human leukocyte antigen-matched brother. Prophylaxis against graft-vs-host disease was performed with cyclosporine A alone. Chimerism of peripheral blood mononuclear cells was evaluated serially using short tandem repeat analysis and flow cytometry.

RESULTS

No meaningful regimen-related toxicities were documented. Donor chimerism of 90 to 100% was achieved on day 14 and thereafter. The patient is doing well, without any recurrence of hemolysis 6 months after transplant. Follow-up chimerism studies confirmed stable and functioning donor-type hematopoiesis.

CONCLUSIONS

NST may become a safe and curative approach in patients with PNH. Further studies are needed to establish the role of NST for treatment of PNH.

Pre-emptive therapy against cytomegalovirus (CMV) disease guided by CMV antigenemia assay after allogeneic hematopoietic stem cell transplantation: a single-center experience in Japan

From April 1998 to March 2000, a cytomegalovirus (CMV) antigenemia-guided pre-emptive approach for CMV disease was evaluated in 77 adult patients who received allogeneic hematopoietic stem cell transplantation at the National Cancer Center Hospital. A CMV antigenemia assay was performed at least once a week after engraftment. High-level antigenemia was defined as a positive result with 10 or more positive cells per 50 000 cells and low-level antigenemia was defined as less than 10 positive cells. Among the 74 patients with initial engraftment, 51 developed positive antigenemia. Transplantation from alternative donors and the development of grade II-IV GVHD were independent risk factors for positive antigenemia. Ganciclovir was administered as pre-emptive therapy in 39 patients in a risk-adapted manner. None of the nine low-risk patients with low-level antigenemia as their initial positive result developed high-level antigenemia even though ganciclovir was withheld. Only one patient developed early CMV disease (hepatitis) during the study period. CMV antigenemia resolved in all but two cases, in whom ganciclovir was replaced with foscarnet. In eight patients, however, the neutrophil count decreased to 0.5 x 10(9)/l or less after starting ganciclovir, including three with documented infections and two with subsequent secondary graft failure. The total amount of ganciclovir and possibly the duration of high-dose ganciclovir might affect the incidence of neutropenia. We concluded that antigenemia-guided pre-emptive therapy with a decreased dose of ganciclovir and response-oriented dose adjustment might be appropriate to decrease the toxicity of ganciclovir without increasing the risk of CMV disease.

Possible clinical benefits of the use of peripheral blood stem cells over bone marrow in the allogeneic transplantation setting for the treatment of childhood leukemia

BACKGROUND

The benefits of allogeneic peripheral blood stem/progenitor cell transplantation (PBSCT) over bone marrow transplantation (BMT), if any, have not been seriously evaluated in a pediatric population. We report here our experience with this procedure and demonstrate rapid engraftment to reduce procedure-related complications and enhanced allogeneic immune reaction to reduce leukemic relapse.

METHODS

The feasibility of PBSCT was reviewed retrospectively. Four patients (2 AML and 2 ALL, aged 8-18 years) underwent allogeneic PBSCT for relapsed leukemia after primary allogeneic BMT (n = 2), for active hepatosplenic fungal abscess (n = 1) or for refractory relapse with conventional chemotherapy (n = 1). Four healthy donors (aged 10-49 years) received granulocyte colony-stimulating factor (G-CSF) 10 microg/kg/day by subcutaneous injection for 5 days. An individualized cytoreductive regimen was used before transplantation.

RESULTS

No significant toxicities were observed in normal donors on G-CSF treatment or at collection of PBSC. After PBSCT, no significant acute toxicities were observed and the median duration to an absolute granulocyte count of 0.5 x 10(9)/l and a platelet count of 20 x 10(9)/l was 16 and 21 days, respectively. Although none of our patients developed acute graft-versus-host disease (GVHD), two developed chronic GVHD involving the liver and skin. Among those who developed chronic GVHD, one died of recurrent disease and another died of pneumonia 235 days after PBSCT. The two remaining patients have been alive without evidence of disease with follow-ups of 193 and 123 days, respectively.

CONCLUSIONS

Allogeneic PBSCT can be a safe procedure in a pediatric population with fewer acute complications, although the potential risk of G-CSF treatment in normal donors should be seriously weighed against the existing risks of marrow aspiration under general anesthesia. The risk of chronic GVHD may need to be balanced against a possible graft-versus-leukemia benefit in patients at higher risk of leukemic relapse.

Generation of dual resistance to 4-hydroperoxycyclophosphamide and methotrexate by retroviral transfer of the human aldehyde dehydrogenase class 1 gene and a mutated dihydrofolate reductase gene

The genetic transfer of drug resistance to hematopoietic cells is an attractive approach to overcoming myelosuppression caused by high-dose chemotherapy. Because cyclophosphamide (CTX) and methotrexate (MTX) are commonly used non-cross-resistant drugs, generation of dual drug resistance in hematopoietic cells that allows dose intensification may increase anti-tumor effects and circumvent the emergence of drug-resistant tumors. We constructed a retroviral vector containing both a human cytosolic ALDH-1 cDNA and a human doubly mutated DHFR cDNA (Phe22/Ser31; termed F/S in the description of constructs) to generate increased resistance to both CTX and MTX. Infection of NIH3T3 cells resulted in increased resistance to both 4-hydroperoxycyclophosphamide (4HC) (1.9 +/- 0.1-fold) and MTX (73 +/- 2.8-fold). Transduced human CD34(+) enriched hematopoietic progenitor cells were also resistant to both 4HC and MTX by CFU-GM readout. Lethally irradiated mice transplanted with SFG-ALDH-IRES-F/S or mock-transduced bone marrow cells were treated with high-dose pulse CTX or high-dose CTX/MTX. Animals receiving marrow not transduced with ALDH-1 or mutated DHFR cDNA died from CTX or CTX/MTX toxicity, whereas mice transduced with ALDH-1 and mutated DHFR cDNA-containing marrow were able to tolerate the same doses of CTX or CTX/MTX treatment posttransplant. These data taken together indicate that ALDH-1 overexpression and mutant DHFR increased both 4HC and MTX resistance in vitro and in the in vivo mouse model. This construct may be useful for protecting patients from high-dose CTX- and MTX-induced myelosuppression.

Delayed recovery of neutrophil counts after peripheral stem cell transplantation which improved with administration of a minimal dose of G-CSF: a case report

G-CSF administration may not affect the rate of engraftment unless sufficient numbers of stem cells are transplanted. However, there might be some cases in which neutrophil recovery is delayed after stem cell transplantation despite a relatively fast recovery of platelet counts and total white blood cell counts. This delayed engraftment might be observed in either autologous or allogeneic stem cell transplantation. Here we report four cases with delayed neutrophil engraftment which subsequently improved with administration of a minimal dose of G-CSF. As the response occurred on the day following G-CSF administration, a mobilization defect is suspected to be the mechanism of this delayed engraftment.

[Non-myeloablative stem cell transplant]

Myeloablation and immunosuppression were considered to be the two major roles of the conditioning regimens for allogeneic stem cell transplantation to facilitate engraftment. It has turned out, however, that immunosuppression is more important and myeloablation is not necessary for engraftment. At the same time, it is considered that the major anti-tumor effect of allogeneic stem cell transplantation depends on the graft-versus-leukemia effect, not on the conditioning regimen itself. In patients with CML who relapsed after allogeneic transplantation, for example, infusion of donor lymphocytes can induce a second complete remission. Non-myeloablative stem cell transplantation (NST) was developed in the late 90s based on these theories. Low-dose, less toxic, so-called "non-myeloablative" preparative regimens have been designed not to eradicate the malignancies, but to provide sufficient immunosuppression to allow donor cells to engraft, while the graft-versus-malignancy effects eradicate the tumor. This strategy permits allogeneic transplantation to be used in patients who are not eligible for conventional, often myeloablative, transplantation because of advanced age or organ dysfunction. Non-myeloablative preparative regimens contain purine analogs, such as fludarabine or cladribine. The NST regimen being used at the National Cancer Center Hospital, Tokyo, Japan, consists of cladribine (0.11 mg/kg x 6 days), busulfan (4 mg/kg x 2 days) and rabbit anti-thymocyte globulin (2.5 mg/kg x 4 days). We enrolled 6 patients in this NST protocol so far: 1 with severe aplastic anemia (sibling-PBSCT), 2 with MDS-RA (1 for sibling-PBSCT and 1 for matched uBMT), 1 with AML-CR2 (matched uBMT), 1 with AML-CR3 (sibling-PBSCT), and 1 with relapsed AML (mismatched related PBSCT). All patients achieved engraftment within 14 days with complete donor chimerism. In addition to leukemias, a graft-versus-malignancy effect was also reported in allogeneic NST of solid tumors, such as renal cell carcinoma and malignant melanoma. The long-term efficacy of NST remains to be determined, and further clinical trials are warranted.

Partially matched transplants with allogeneic CD34+ blood cells

Allogeneic CD34(+) selected cell transplantation from a partially matched donor is feasible for the treatment of hematopoietic malignancies. Severe graft-versus-host disease (GvHD) can be prevented by this approach, and a lengthy search for an unrelated donor can be avoided. However, long-term engraftment is still a challenge, and may require intensified conditioning regimens with severe toxicities to sustain engraftment. Furthermore, unacceptable effects such as relapse and life-threatening viral infections might be more frequent after such transplants compared with non-T-cell-depleted transplants from an HLA-identical donor. Strict indications should be considered for this treatment based on a risk/benefit assessment for very high-risk patients. The early application of periodic donor leukocyte infusion (DLI) may be useful for preventing both late graft rejection and serious viral infections.