Late hemorrhagic cystitis after reduced-intensity hematopoietic stem cell transplantation (RIST)

Pretransplant BK Virus-Specific T-Cell-Mediated Immunity and Serotype Specific Antibodies May Have Utility in Identifying Patients at Risk of BK Virus-Associated Haemorrhagic Cystitis after Allogeneic HSCT

BK polyomavirus (BKPyV) persists lifelong in renal and urothelial cells with asymptomatic urinary shedding in healthy individuals. In some immunocompromised persons after transplantation of hematopoietic stem cells (HSCT), the BKPyV high-rate replication is associated with haemorrhagic cystitis (HC). We tested whether the status of BKPyV immunity prior to HSCT could provide evidence for the BKPyV tendency to reactivate. We have shown that measurement of pretransplant anti-BKPyV 1 and 4 IgG levels can be used to evaluate the HC risk. Patients with anti-BKPyV IgG in the range of the 1st-2nd quartile of positive values and with positive clinical risk markers have a significantly increased HC risk, in comparison to the reference group of patients with "non-reactive" anti-BKPyV IgG levels and with low clinical risk (LCR) (p = 0.0009). The predictive value of pretransplant BKPyV-specific IgG was confirmed by determination of genotypes of the shed virus. A positive predictive value was also found for pretransplant T-cell immunity to the BKPyV antigen VP1 because the magnitude of IFN-γ T-cell response inversely correlated with posttransplant DNAuria and with HC. Our novel data suggest that specific T-cells control BKPyV latency before HSCT, and in this way may influence BKPyV reactivation after HSCT. Our study has shown that prediction using a combination of clinical and immunological pretransplant risk factors can help early identification of HSCT recipients at high risk of BKPyV disease.

Effectiveness of hyperbaric oxygen therapy for virus-associated hemorrhagic cystitis after allogeneic hematopoietic stem cell transplantation

Although some studies have suggested the effectiveness of hyperbaric oxygen (HBO) therapy for hemorrhagic cystitis (HC) after allogeneic hematopoietic stem cell transplantation (HSCT), the role of HBO has not been established. We compared the treatment outcomes of 8 patients with viral HC (adenovirus [ADV], n = 2; BK virus [BKV], n = 6) treated with HBO (HBO[+]) and 8 patients (ADV, n = 2; BKV, n = 6) treated with conventional therapy (HBO[−]), such as urinary catheterization and intravenous cidofovir. HBO therapy was performed at 2.1 atmospheres for 90 min/day until clinical improvement was achieved. The median number of HBO treatments was 10 (range 8–12). The median duration of HBO treatment was 19.5 days (range 10–23 days). All 8 HBO(+) patients achieved complete remission (CR) at a median of 14.5 days (range 5–25 days). Of the 8 HBO(−) patients, 5 (62.5%) obtained CR and 3 remained symptomatic for 2–6 months. The cumulative incidence of transplant-related mortality at day 100 after allogeneic HSCT was significantly higher in the HBO(−) patients than in the HBO(+) patients (14.2 vs. 0%, P < 0.05). No severe HBO-related adverse effects were observed. In conclusion, HBO is a feasible option for treating viral HC after allogeneic HSCT.

Reactivation of polyomavirus in the genitourinary tract is significantly associated with severe GvHD and oral mucositis following allogeneic stem cell transplantation

PURPOSE

BK-virus and JC-virus are the most common polyomaviridae associated with hemorrhagic cystitis in the allogeneic transplant setting. Hemorrhagic cystitis and symptomatic viruria caused by these viruses are a major cause of morbidity in patients undergoing allogeneic stem cell transplantation.

METHODS

We performed a retrospective evaluation on a highly uniform study population of 73 patients receiving allogeneic stem cell transplantation. Patients were treated according to the FLAMSA-RIC-protocol, and were examined for the incidence of BK-/JC-viruria and late-onset BK-positive hemorrhagic cystitis within a two-year period.

RESULTS

The occurrence of BK-viruria was correlated with published risk factors (acute GvHD, oral mucositis, donor type, conditioning, age, gender). Thirty patients (41 %) were found to excrete either BK-virus (n = 17), JC-virus (n = 3) or both (n = 10), of whom 18 patients (60 %) developed higher-grade hemorrhagic cystitis as opposed to none in the virus-negative control group. Higher grade GvHD (grade B-D) was more common in patients with viruria (p = 0.013) and also more common in patients with manifest hemorrhagic cystitis (p = 0.048). Similarly, oral mucositis was associated both with viruria (p = 0.014) and hemorrhagic cystitis (p = 0.005). Manifest cystitis but not viruria was significantly associated with male gender (p = 0.016). No significant correlation was found with age, conditioning with busulfane vs total body irradiation or related vs unrelated donor.

CONCLUSIONS

Severe GvHD and oral mucositis are significantly associated with reactivation of polyomaviridae in the genitourinary-tract already at the level of asymptomatic viruria.

The polyomavirus puzzle: is host immune response beneficial in controlling BK virus after adult hematopoietic cell transplantion?

BK virus (BKV), a ubiquitous human polyomavirus, usually does not cause disease in healthy individuals. BKV reactivation and disease can occur in immunosuppressed individuals, such as those who have undergone renal transplantation or hematopoietic cell transplantation (HCT). Clinical manifestations of BKV disease include graft dysfunction and failure in renal transplant recipients; HCT recipients frequently experience hematuria, cystitis, hemorrhagic cystitis (HC), and renal dysfunction. Studies of HCT patients have identified several risk factors for the development of BKV disease including myeloablative conditioning, acute graft-versus-host disease, and undergoing an umbilical cord blood (uCB) HCT. Although these risk factors indicate that alterations in the immune system are necessary for BKV pathogenesis in HCT patients, few studies have examined the interactions between host immune responses and viral reactivation in BKV disease. Specifically, having BKV immunoglobulin-G before HCT does not protect against BKV infection and disease after HCT. A limited number of studies have demonstrated BKV-specific cytotoxic T cells in healthy adults as well as in post-HCT patients who had experienced HC. New areas of research are required for a better understanding of this emerging infectious disease post HCT, including prospective studies examining BK viruria, viremia, and their relationship with clinical disease, a detailed analysis of urothelial histopathology, and laboratory evaluation of systemic and local cellular and humoral immune responses to BKV in patients receiving HCT from different sources, including uCB and haploidentical donors.

BK virus disease after allogeneic stem cell transplantation: a cohort analysis

The clinical epidemiology of BK virus (BKV) disease after allogeneic hematopoietic stem cell transplantation (HSCT) is not well defined. We evaluated 491 patients transplanted from January 2010 to December 2011 at a single transplant center to assess incidence, severity, and risk factors for BKV disease after HSCT. BKV disease was defined as BKV detection in urine by PCR testing in association with genitourinary symptoms without other concurrent genitourinary conditions. BKV disease occurred in 78 patients (15.9%), for an incidence rate of .47/1000 patient-days (95% confidence interval [CI], .37 to .59); BKV disease was considered severe in 27 patients (5.5%). In multivariate Cox modeling, time-dependent acute graft-versus-host disease (aGVHD) grades II to IV (adjusted hazard ratio [aHR] 4.25; 95% CI, 2.51 to 7.21), cord blood HSCT (aHR 2.28; 95% CI, 1.01 to 5.15), post-transplant mycophenolate use (aHR 3.31; 95% CI, 1.83 to 5.99), and high-dose cyclophosphamide conditioning (aHR 2.34, 95% CI 1.45 to 3.77) were significant predictors of BKV disease. Time-dependent aGVHD grades III to IV (aHR 10.5; 95% CI, 4.44 to 25.0) and cord blood HSCT (aHR 5.40; 95% CI, 1.94 to 15.0) were independent risk factors for severe BKV disease. BKV disease is common and is associated with significant and prolonged morbidity after HSCT. Prospective studies are needed to better define the morbidity of post-HSCT BKV disease and inform the design of prophylaxis and treatment trials.

Cytomegalovirus is a potential risk factor for late-onset hemorrhagic cystitis following allogeneic hematopoietic stem cell transplantation

Late-onset hemorrhagic cystitis (LOHC) is a common complication following allogeneic hematopoietic stem cell transplantation (allo-HSCT) and is primarily associated with viral infection. We prospectively quantified cytomegalovirus (CMV), BK virus (BKV), and adenovirus in urine and plasma using Q-RT-PCR in 50 consecutive patients to define the relationship between virus and LOHC. Of the 50 patients, 21 developed LOHC at a median of 29 days (range 4-64 days), with a cumulative incidence of 42% (±7.1%). The cumulative incidence of LOHC on day 100 in patients with and without CMV viremia (prior to or at the onset of LOHC) were 56.3% (±8.9%) and 16.7% (±9.1%) (P = 0.018), respectively, and it was 59.3% (±9.8%) and 21.7% (±8.8%) in patients with and without CMV viruria (prior to or at the onset of LOHC) (P = 0.021), respectively. The cumulative incidence of LOHC was also higher in patients with a plasma BKV load increased ≥3 log10 or with a urine BKV load increased ≥4 log10 than those without the increase (P < 0.001). Only one patient with LOHC was tested positive for ADV. Both the univariate and multivariate analyses showed that CMV viremia (HR = 3.461, 95% CI: 1.005-11.922, P = 0.049) and a plasma BKV load that was increased ≥3 log10 (HR = 10.705, 95%CI: 2.469-46.420, P = 0.002) were independent risk factors for the development of LOHC. We conclude that both CMV viremia and an increase of plasma BKV are independent risk factors for LOHC. And the role of CMV viremia was firstly demonstrated.

BK viremia precedes hemorrhagic cystitis in children undergoing allogeneic hematopoietic stem cell transplantation

BK virus is associated with hemorrhagic cystitis after hematopoietic stem cell transplantation (HSCT), although evidence supporting a causal relationship remains limited. Although BK viruria is common after HSCT, BK viremia may better predict clinically significant cystitis, similar to its predictive value for nephropathy after kidney transplantation. We hypothesized that BK viremia would precede hemorrhagic cystitis in a cohort of 88 consecutive children prospectively enrolled to originally study thrombotic microangiopathy in the first 100 days after allogeneic HSCT. Cox regression models with time-varying covariates assessed the association between different BK viremia cutoffs and the development of hemorrhagic cystitis, defined as at least macroscopic hematuria. Subjects with a peak plasma BK viral load 1 to 9999 copies/mL had an adjusted hazard ratio of 4.2 (95% confidence interval (CI), 1.3 to 13.7) for the development of hemorrhagic cystitis. Those with peak BK viremia >100,000 copies/mL had an adjusted hazard ratio of 116.8 (95% CI, 12 to 1136) for cystitis. Other independent risk factors for hemorrhagic cystitis included age >7 years and HHV-6 viremia. Neither graft-versus-host disease nor achieving engraftment increased the risk for cystitis. If therapeutic strategies are found to be effective, these observations may support screening for BK viremia after HSCT, as currently recommended for other DNA viruses.

Different risk factors related to adenovirus- or BK virus-associated hemorrhagic cystitis following allogeneic stem cell transplantation

Virus-associated hemorrhagic cystitis (HC) is a major cause of morbidity and mortality following allogeneic hematopoietic stem cell transplantation (HSCT). Although numerous studies have attempted to identify factors that predispose patients to viral HC, its causes remain controversial. We analyzed retrospectively the results of 266 allogeneic HSCTs to identify factors associated with HC. Of this group, 42 patients (15.8%) were diagnosed with viral HC, because of either adenovirus (ADV; n = 26; 9.8%) or BK virus (BKV; n = 16; 6.0%). ADV-HC was frequently associated with T cell purging, and was less common in patients with acute graft-versus-host-disease (GVHD). Conversely, BKV-HC was more frequently observed in patients with excessive immune reactions such as GVHD, preengraftment immune reaction, and hemophagocytic syndrome. These observations indicate that ADV- and BKV-HC may differ significantly in their risk factors and pathogenesis. Profound immune deficiency is more likely to be associated with ADV-HC, whereas immune hyperactivity might play a key role in BKV-HC.

Management of refractory hemorrhagic cystitis following hematopoietic stem cell transplantation in children

HC is a complication associated with HSCT, but occurs rarely in solid organ recipients. The reported incidence varies from <10% to more than 70%. HC is characterized by hemorrhagic inflammation in urinary tract mucosa with symptoms varying from asymptomatic microscopic hematuria to frank hematuria with clot formation and urinary tract obstruction. Early onset HC may be explained by toxicity of chemo- and/or radiotherapy, while multiple factors including viral infections and their interplay seem to be involved in late onset HC. So far, only incidence of cyclophosphamide-associated HC has been reduced with preventive treatment. Likely, once HC is established, the treatment principles are similar regardless of the etiology and depend on the intensity of HC. Prevention of urinary tract obstruction, transfusion support, analgesic, and spasmolytic therapy are generally accepted in HC management. Treatment beyond this conservative approach entails higher risk for side effects, and thus treatment escalation proportional to HC intensity is warranted. No standard and evidence-based treatment escalation algorithm has been widely adopted yet. As severe HC following HSCT is a potentially life-threatening complication, a multidisciplinary and individual approach is required in children suffering from this devastating complication.

Late onset hemorrhagic cystitis in a hematopoietic stem cell recipient: treatment with intravesical hyaluronic acid

HC is a common complication following HSCT. Risk factors include viral infections, cyclophosphamide and busulfan usage, pelvic irradiation, older age at transplantation, allogeneic HSCT and GvHD. The severity of HC ranges from mild hematuria to life-threatening bleeding. Here, we present a seven-and-a-half-yr-old boy with Wiskott-Aldrich syndrome who experienced a late onset Grade III hemorrhagic cystitis following HSCT from his fully matched sibling. A Grade I GvHD localized to skin developed on day +11 and prednisolone therapy was given between the 11th and 22nd d. Myeloid and platelet engraftments were achieved +13 and +16 d, respectively. A gross hematuria began on the 21st post-transplant day. The urine cultures for bacterial or fungal organisms were negative. Urine analysis by PCR revealed a CMV viruria. Following systemic ganciclovir treatment, urinary CMV became negative but hemorrhagic cystitis did not improve. Due to the probability of existing BK virus or adenovirus, two doses of cidofovir were administered intravesically. As he continued to have painful hematuria with large clot formations, two doses of intravesical hyaluronic acid were applied. Macroscopic hematuria resolved within four d after the second dose. Complete remission was achieved on day +77. Finally, intravesical administration of hyaluronic acid seems to be effective and safe and can be a promising treatment in patients suffering from severe and late onset HC.

Hemorrhagic cystitis after allogeneic hematopoietic stem cell transplants is the complex result of BK virus infection, preparative regimen intensity and donor type

BACKGROUND

Hemorrhagic cystitis is a common cause of morbidity after allogeneic stem cell transplantation, frequently associated with BK virus infection. We hypothesized that patients with positive BK viruria before unrelated or mismatched related donor allogeneic hematopoietic stem cell transplantation have a higher incidence of hemorrhagic cystitis.

DESIGN AND METHODS

To test this hypothesis, we prospectively studied 209 patients (median age 49 years, range 19-71) with hematologic malignancies who received bone marrow (n=78), peripheral blood (n=108) or umbilical cord blood (n=23) allogeneic hematopoietic stem cell transplantation after myeloablative (n=110) or reduced intensity conditioning (n=99). Donors were unrelated (n=201) or haploidentical related (n=8).

RESULTS

Twenty-five patients developed hemorrhagic cystitis. Pre-transplant BK viruria detected by quantitative PCR was positive in 96 patients. The one-year cumulative incidence of hemorrhagic cystitis was 16% in the PCR-positive group versus 9% in the PCR-negative group (P=0.1). The use of umbilical cord blood or a haploidentical donor was the only significant predictor of the incidence of hemorrhagic cystitis on univariate analysis. There was also a trend for a higher incidence after myeloablative conditioning. Multivariate analysis showed that patients who had a positive PCR pre-transplant and received haploidentical or cord blood grafts with myeloablative conditioning had a significantly higher risk of developing hemorrhagic cystitis (58%) than all other recipients (7%, P<0.001).

CONCLUSIONS

Hemorrhagic cystitis is the result of a complex interaction of donor type, preparative regimen intensity, and BK viruria.

Cyclophosphamide and cancer: golden anniversary

Cyclophosphamide remains one of the most successful and widely utilized antineoplastic drugs. Moreover, it is also a potent immunosuppressive agent and the most commonly used drug in blood and marrow transplantation (BMT). It was initially synthesized to selectively target cancer cells, although the hypothesized mechanism of tumor specificity (activation by cancer cell phosphamidases) transpired to be irrelevant to its activity. Nevertheless, cyclophosphamide's unique metabolism and inactivation by aldehyde dehydrogenase is responsible for its distinct cytotoxic properties. Differential cellular expression of aldehyde dehydrogenase has an effect on the anticancer therapeutic index and immunosuppressive properties of cyclophosphamide. This Review highlights the chemistry, pharmacology, clinical toxic effects and current clinical applications of cyclophosphamide in cancer and autoimmune disorders. We also discuss the development of high-dose cyclophosphamide for BMT and the treatment of autoimmune diseases.

Prevention and management of BK-virus associated haemorrhagic cystitis in children following haematopoietic stem cell transplantation--a systematic review and evidence-based guidance for clinical management

Haemorrhagic cystitis (HC) is a common and, in its severe form, potentially life-threatening complication of Haematopoietic stem cell transplantation (HSCT) in children. Recent data indicate an important role of BK virus reactivation during the time of maximal post-transplant immune suppression in the pathogenesis of late-onset HC. Treatment of HC is mainly symptomatic and often frustrating. To give clinicians guidance on prevention and treatment options and their backing by scientific evidence, we have systematically assessed the available literature and devised evidence-based guidelines. Our comprehensive review demonstrates that evidence for the most commonly used interventions (such as cidofovir, oestrogen, hyperbaric oxygen, bladder instillation with formalin, alum salts or prostaglandin) is very limited. Some of these interventions also carry significant risks. Higher level evidence exists only for 2-mercaptoethane sodium (MESNA) and hyperhydration as a preventative intervention, and for systemic recombinant Factor VII as a treatment to stop acute haemorrhage. Further high-quality studies are required to establish effective and safe prevention and treatment options for HC.

BK-viruria and haemorrhagic cystitis are more frequent in allogeneic haematopoietic stem cell transplant patients receiving full conditioning and unrelated-HLA-mismatched grafts

The influence of conditioning regimen, donor background and HLA matching on development of BK virus (BKV)-associated haemorrhagic cystitis (HC) was examined in 175 allogeneic haematopoietic stem cell transplant (HSCT) patients, undergoing 179 HSCT events. Twenty-seven patients presented late-onset HC, and BK viruria was verified in 23/27 HC events. Seventy-one (40%) HSCTs were performed with myeloablative conditioning (MC), 108 (60%) were performed with reduced intensity conditioning (RIC), 66 (37%) were performed with a related donor (RD) grafts and 113 (63%) with an unrelated donor (URD) graft. BK viruria was more common during HC, than non-HC events, after MC as compared to RIC (both P<0.001), and with an HLA-mismatched donor (P<0.01). By multivariate logistical regression analysis, independent risk factors for HC were BKV (OR 6.7; 95% CI 2.0-21.7; P=0.001), MC (OR 6.0; 95% CI 2.1-17.3; P<0.001) and URD (OR 3.4; 95% CI 1.1-10.6; P=0.03). However, when analysing HSCT performed with URD or RD grafts separately, BKV (OR 8.5; 95% CI 1.8-19.3; P=0.004) and MC (OR 5.9; 95% CI 1.3-11.3; P=0.009) increased the risk for HC only with a URD, but not with an RD graft.

Hyperbaric oxygen should not be used in the management of hemorrhagic cystitis in patients with Fanconi anemia

Hemorrhagic cystitis (HC) is a common complication after stem cell transplantation (SCT) that occurs more frequently in patients with Fanconi anemia (FA) because of hypersensitivity of their cells to the agents used in the preparation for SCT (chemo and radiation). Many HC cases respond to therapy with hyperhydration and maintenance of adequate platelet counts, but refractory cases may require additional measures such as the use of prostaglandins, alum, or hyperbaric oxygen (HBO). We report here an unusual complication to HBO therapy in a FA patient consisting of generalized edema mimicking capillary leak syndrome but with no pulmonary edema or ascites.

Critical care considerations of hematopoietic stem cell transplantation

OBJECTIVE

To review the available clinical data on the critical care complications of hematopoietic stem cell transplantation (HSCT).

DATA SOURCE

The MEDLINE database and references from the identified articles related to the critical care in HSCT.

CONCLUSION

HSCT is an important treatment for a variety of malignant and nonmalignant conditions. The procedure is, however, limited by significant complications that may involve every organ of the body. Up to 40% of HSCT recipients are admitted to the intensive care unit as a result of severe complications related to the transplantation. The outcome of those critically ill patients has been traditionally poor. However, recent advances in the transplantation procedure, diagnostic studies, antimicrobial prophylaxis and therapy, and intensive care unit care have improved the outcome of these patients. The increasing number of HSCTs performed annually, the unique complications that develop in these patients, and the improvement in the intensive care unit outcome make knowledge about the critical care aspect of HSCT an essential part of the current practice of critical care medicine.

Reduced-intensity conditioning for acute myeloid leukemia: is this strategy correct

Allogeneic stem cell transplantation for acute myeloid leukemia (AML) using reduced-intensity conditioning (RIC) is based on the strategy of attaining donor cell engraftment with immunosuppressive agents. This approach, which relies predominantly on donor effector cells for anti-leukemic or graft-versus-leukemia effect, is being used with increased frequency. Treatment-related mortality appears less with RIC than that observed with conventional myeloablative regimens. Available data support the fact that a myeloablative regimen is not required for successful engraftment and some patients appear to be cured of their disease. Despite the plethora of clinical reports, however, no prospective studies have been conducted that establish this procedure as the preferred option in AML. On the other hand, patients formerly excluded from a myeloablative procedure such as the 'elderly' and those with significant comorbid conditions, often may be RIC transplant candidates. By using prospective controlled clinical trials, we will determine whether these encouraging RIC data are applicable to a nonselect population of AML. The transplant community now is poised to design and complete investigations to ascertain the true role of RIC in the treatment of AML.

Polyoma BK virus and haemorrhagic cystitis in haematopoietic stem cell transplantation: a changing paradigm

Haemorrhagic cystitis (HC) is a distinct clinical disorder of multiple aetiologies. It is characterized by painful haematuria due to haemorrhagic inflammation of the urinary bladder mucosa. In allogeneic haematopoietic stem cell transplantation (HSCT), HC occurring before engraftment is mostly transient and self-limiting, whereas that after engraftment is severe and sometimes life-threatening. Pre- and post-engraftment HC represent distinct disorders with different aetiologies and treatment implications. Recent data suggest that reactivation of the polyoma BK virus (BKV) plays a pivotal role in post-engraftment HC. Urotoxicity of the conditioning regimen and alloimmune reaction accompanying graft-versus-host disease (GVHD) upon engraftment are also important pathogenetic factors. Based on data from BKV studies, we propose that HC may be divided into three phases. In the first phase, the conditioning regimen damages uroepithelial cells, providing a milieu for BKV replication. In the second phase, unchecked uroepithelial BKV replication leads to BK viruria. In the last phase after engraftment, alloimmunity against BKV-infected uroepithelial cells leads to HC. The quinolone antibiotics suppress BKV replication in vivo and in vitro, suggesting that their prophylactic use may prevent the occurrence of HC.

Comparison between reduced intensity and conventional myeloablative allogeneic stem-cell transplantation in patients with hematologic malignancies aged between 50 and 59 years

To evaluate the efficacy of reduced-intensity stem-cell transplantation (RIST), we retrospectively compared outcomes of 207 consecutive Japanese patients aged between 50 and 59 years with hematologic malignancies who received RIST (n=70) and conventional stem-cell transplantation (CST) (n=137). CST recipients received total body irradiation (TBI)-based or busulfan/cyclophosphamide-based regimens. RIST regimens were purine analog-based (n=67), 2 Gy TBI-based (n=2), and others (n=1). Most CST recipients (129/137) received calcineurin inhibitors and methotrexate as graft-versus-host (GVHD) prophylaxis, while 32 RIST recipients received cyclosporin. In all, 23 CST and five RIST recipients died without disease progression within 100 days of transplant. Grade II to IV acute GVHD occurred in 56 CST and 38 RIST recipients. There was no significant difference in overall survival (OS) and progression-free survival between CST and RIST. On multivariate analysis on OS, five variables were significant: preparative regimens (CST vs RIST) (hazard ratio=1.92, 95% confidence interval, 1.25-2.97; P=0.003), performance status (2-4 vs 0-1) (2.50, 1.51-4.16; P<0.001), risk of underlying diseases (1.85, 1.21-2.83; P=0.004), acute GVHD (2.57, 1.72-3.84; P<0.001), and CML (0.38, 0.21-0.69; P=0.002). We should be careful in interpreting results of this small-sized retrospective study; however, reduced regimen-related toxicity might contribute to better survival in RIST. The low relapse rates following RIST suggest a strong antitumor activity through allogeneic immunity.