Eradication of virus-infected T-cells in a case of adult T-cell leukemia/lymphoma by nonmyeloablative peripheral blood stem cell transplantation with conditioning consisting of low-dose total body irradiation and pentostatin

Striving to cure adult T-cell leukaemia/lymphoma: a role for allogeneic stem cell transplant?

Adult T-cell leukaemia/lymphoma (ATL) is an aggressive HTLV-1-related malignancy, rare outside of regions where the retrovirus is endemic. Although the use of antiviral therapy has improved outcomes, particularly for indolent forms of ATL, response to combination chemotherapy is poor and outcomes for aggressive subtypes remains dismal. Consolidation with allogeneic stem cell transplant (alloSCT) has an increasing role in the management of ATL in eligible patients, offering favourable long-term remission rates. However, relatively high-transplant-related mortality and issues with donor recruitment for certain ethnicities remain problematic. In this review, we discuss the rationale for and issues surrounding alloSCT in ATL in the context of conventional and emerging therapies.

Allogeneic stem cell transplantation for adult T-cell leukemia/lymphoma

Adult T-cell leukemia/lymphoma (ATLL) develops in elderly individuals who have been infected with human T-cell leukemia virus type 1 (HTLV-1), and the prognosis for patients with ATLL has been extremely poor. Retrospective studies of allogeneic stem cell transplantation (alloSCT) for selected populations of patients have achieved several encouraging results; however, the reported incidence of transplantation-related mortality (TRM) have been high, even though more than 80% of patients received stem cells from related donors and the patients were relatively young for ATLL. This report documents a prospective feasibility study of alloSCT with reduced-intensity conditioning (RIST) for elderly ATLL patients (>50 years). Regimen-related toxicities and nonhematologic toxicities were acceptable. Fourteen of 15 evaluable patients achieved complete donor chimerism within 90 days, and 1 patient had early TRM after RIST. The HTLV-1 proviral load became undetectable in 8 of 15 patients, suggesting that RIST has potential as an antiviral treatment. The results of alloSCT are promising, and 30% to 40% of patients who achieve remission and have suitable donors can now become long-term survivors with either conventional alloSCT or RIST. It is clear that a graft-versus-ATLL effect is present after alloSCT, regardless of the conditioning regimen or the stem cell source.

Risk assessment in haematopoietic stem cell transplantation: viral status

Viral infections have been important complications in the transplant procedure from the early days of stem-cell transplantation, causing significant morbidity and mortality. It is important for the management of patients to assess the risk for viral infections that might develop after the stem-cell transplantation. This can be exemplified by cytomegalovirus (CMV) and other herpesviruses, but risk assessment is also important for other viral infections. The aim of this review is to describe current knowledge regarding recipient and donor serological status for viral infections.

The human T-cell leukemia virus type 1 (HTLV-1): New insights into the clinical aspects and molecular pathogenesis of adult t-cell leukemia/lymphoma (ATLL) and tropical spastic paraparesis/HTLV-associated myelopathy (TSP/HAM)

Human T-cell leukemia virus type 1 (HTLV-1) was the first human retrovirus to be identified in the early 1980s. The isolation and identification of a related virus, HTLV-2, and the distantly related human immunodeficiency virus (HIV) immediately followed. Of the three retroviruses, two are associated definitively with specific diseases, HIV, with acquired immune deficiency syndrome (AIDS) and HTLV-1, with adult T-cell leukemia/lymphoma (ATLL) and tropical spastic paraparesis/HTLV-1-associated myelopathy (TSP/HAM). While an estimated 10-20 million people worldwide are infected with HTLV-I, infection is endemic in the Caribbean, parts of Africa, southwestern Japan, and Italy. Approximately 4% of HTLV-I infected individuals develop ATLL, a disease with a poor prognosis. The clinical manifestations of infection and the current biology of HTLV viruses with emphasis on HTLV-1 are discussed in detail. The implications for improvements in diagnosis, treatment, intervention, and vaccination are included, as well as a discussion of the emergence of HTLV-1 and -2 as copathogens among HIV-1-infected individuals.

Bone marrow transplantation from unrelated donors for patients with adult T-cell leukaemia/lymphoma

Adult T-cell leukaemia/lymphoma (ATLL) is a highly aggressive haematological malignancy. More than 40 cases of ATLL treated by allogeneic bone marrow transplantation (BMT) from sibling donors have been reported, while there have been only a few cases of unrelated BMT for treatment of this disease. We began performing allogeneic BMT from unrelated donors in 1999 to improve the outcome of ATLL patients with no suitable sibling donors. Eight ATLL patients underwent unrelated BMT; five received the conventional conditioning regimen consisting of cyclophosphamide and total body irradiation, while three received a reduced-intensity preparative regimen. Two patients died due to encephalopathy of unknown aetiology on days 10 and 35, and one patient died due to progression of ATLL 25 months after BMT. Five patients are currently alive and disease-free at a median of 20 months after BMT. Proviral human T-lymphotropic virus type-I (HTLV-I) DNA load in peripheral blood mononuclear cells (PBMCs) was assessed in four cases before and after BMT. HTLV-I proviral DNA load was reduced significantly after transplantation. Unrelated BMT is feasible for treatment of ATLL. Further studies in a larger number of cases are required to determine the optimal conditioning regimen and stem cell source.

Durable hematologic complete response and suppression of HTLV-1 viral load following alemtuzumab in zidovudine/IFN-{alpha}-refractory adult T-cell leukemia

Adult T-cell leukemia (ATL) is a highly chemoresistant and usually fatal T-cell malignancy due to the human T-cell lymphotropic virus-1 (HTLV-1). After chemotherapy failure, antiretrovirals and interferon-alpha (IFN-alpha) produce brief responses followed by progression and death. More effective agents and new approaches to detect and treat minimal residual disease are needed. ATL cells express CD52, the target of the antibody alemtuzumab, which is active in a preclinical model of ATL and is cytotoxic for p53-deficient cells. A patient with refractory chronic ATL in transformation achieved longer than a 1-year complete hematologic response following 12 weeks of outpatient subcutaneous alemtuzumab. Persistent suppression of HTLV-1 viral load, even at recovery of T cells, after alemtuzumab and efficient in vitro complement-mediated cytotoxicity of primary ATL cells with mutated TP53 were observed. The unprecedented response and the profound suppression of HTLV-1 viral load observed in this patient suggest that further clinical investigation of alemtuzumab in ATL is warranted.

Expression of Human Tumor-Associated Antigen RCAS1 in Adult T-Cell Leukemia/Lymphoma

In human cancer, RCAS1 (the receptor-binding cancer antigen expressed on SiSo cells) on the surface of various kinds of tumor cells reportedly induces the apoptosis of T-cells and natural killer cells, resulting in evasion of the immune system. In the present study, an immunohistochemical analysis of RCAS1 expression was performed with lymph node specimens obtained from patients with adult T-cell leukemia/lymphoma (ATLL). Positive staining was seen in 15 (75%) of 20 cases and in all cases of patients with short survival times. In the cases of B-cell lymphomas, positive staining was seen in only 1 (13%) of 8 cases. These findings indicate that expression of RCAS1 may be associated with the evasion from immune surveillance of cells infected with human T-lymphotropic virus type I, resulting in the development of overt leukemia/lymphoma. Determination of RCAS1 expression may be useful for predicting the prognosis of patients with ATLL.

Current Status of Therapeutic Approaches to Adult T-Cell Leukemia

More than 2 decades have elapsed since the proposal of adult T-cell leukemia (ATL). Since then, the discovery of the etiologic virus, human T-cell leukemia virus type I (HTLV-I), and the establishment of the diagnostic steps of serum test and molecular study have clearly defined ATL as a distinct disease entity. Because conventional chemotherapy, which is active against other lymphoid malignancies, was proven to be ineffective for treating aggressive forms of ATL, ATL has become the target of several clinical studies for the purpose of improving therapeutic outcomes. Combination chemotherapy exclusively designed for ATL has considerably elevated the treatment response rate in ATL patients, but it has not sufficiently extended the median survival time. The introduction of antiviral agents has led to surprising effects for patients with acute ATL. Monoclonal antibodies seem to be promising, especially for patients with chemotherapy-resistant disease. Unfortunately, these approaches did not prove to be sufficient for most patients with ATL to obtain long-term survival. Recent promising reports on allogeneic stem cell transplantation (allo-SCT) for ATL have suggested that allo-SCT could overcome the limitations that other treatment modalities have not surmounted. More efforts are clearly needed to clarify the usefulness of allo-SCT, especially with reduced-intensity conditioning regimens, for ATL patients.

Phase II study of cladribine (2-chlorodeoxyadenosine) in relapsed or refractory adult T-cell leukemia-lymphoma

Adult T-cell leukemia-lymphoma (ATL) is a retrovirus-associated T-cell malignancy with an extremely poor prognosis; the median survival time of ATL patients with the acute or lymphoma type is less than 1 year with various combination chemotherapies. Cladribine (2-chlorodeoxyadenosine; 2-CdA), a purine analog resistant to degradation by adenosine deaminase, has shown definitive clinical activity against various lymphoid malignancies, including hairy cell leukemia, indolent lymphoma, and cutaneous T-cell lymphoma. An in vitro study showed the sensitivity of T-lymphoblastoid cell lines to cladribine, and a preceding Japanese phase I study of cladribine showed that 1 refractory patient with ATL achieved an objective response. To evaluate the therapeutic efficacy of cladribine in treating ATL, we conducted a multicenter phase II study. The plan was to administer cladribine to 30 ATL patients as 0.09 mg/kg per day by 7-day continuous intravenous infusion every 4 weeks for up to 3 courses. Before the planned interim analysis, 16 patients with relapsed or refractory ATL were enrolled, 15 of whom were eligible. Only 1 of the 15 eligible patients showed an objective response (overall response rate, 7%; 90% confidence interval, 0% to 28%), and 11 patients (73%) showed progressive disease, mostly during the first course of treatment. Because the upper limit of the 90% confidence interval of the overall response rate did not reach 30% in the interim analysis, the Independent Monitoring Committee advised us to discontinue patient enrollment. In conclusion, cladribine is not worthy of further investigation for the treatment of ATL.

Deoxycoformycin-containing combination chemotherapy for adult T-cell leukemia-lymphoma: Japan Clinical Oncology Group Study (JCOG9109)

Aggressive adult T-cell leukemia-lymphoma (ATL) generally has a very poor prognosis. Deoxycoformycin (DCF, pentostatin), an inhibitor of adenosine deaminase, has shown promising therapeutic efficacy for ATL. To develop a new effective therapy against aggressive ATL, we carried out a multicenter phase II study of DCF-containing combination chemotherapy. Sixty-two previously untreated patients with ATL (34, 21, and 7 patients with diseases of the acute, lymphoma, and unfavorable chronic types, respectively) were enrolled, but 2 were ineligible because they were judged to be favorable chronic types. A regimen of 1 mg/m2 vincristine intravenously on days 1 and 8, 40 mg/m2 doxorubicin intravenously on day 1, 100 mg/m2 etoposide intravenously on days 1 through 3, 40 mg/m2 prednisolone orally on days 1 and 2, and 5 mg/m2 DCF intravenously on days 8, 15, and 22 was administered every 28 days for 10 cycles unless disease progression or toxic complications occurred. Fifty-two percent of 60 eligible patients responded (95% confidence interval [CI], 38%-65%), with 17 patients (28%) achieving a complete response (CR) (95% CI, 17%-41%) and 14 achieving a partial response. The CR rate was inferior to those of both the previous Japan Clinical Oncology Group (JCOG) study (JCOG8701, 43%), a 9-drug combination chemotherapy of the second generation, and the subsequent JCOG9303 study (35%), a granulocyte colony-stimulating factor-supported, dose-intensified, 9-drug regimen. The median survival time of the 60 eligible patients in JCOG9109 was 7.4 months, and the estimated 2-year survival rate was 15.5%; these results were identical with those of JCOG8701 but inferior to those of JCOG9303. Grade 4 neutropenia and infection of grade 3 or greater were frequent (67% and 22%, respectively), and treatment-related death was observed in 4 patients (7%), septicemia in 2, and cytomegalovirus pneumonia in 2. We conclude that DCF-containing combination chemotherapy is not a promising regimen against aggressive ATL.