Stem cell transplantation for chronic lymphocytic leukemia: different outcome after autologous and allogeneic transplantation and correlation with minimal residual disease status

Allogeneic transplantation for high-risk chronic lymphocytic leukemia-a summary of a 16-year experience

In the pathway inhibitor era, the number of allogeneic stem cell transplantation (ASCT) for chronic lymphocytic leukemia (CLL) continues to decrease and this approach should be offered only after careful risk-benefit assessment. Nevertheless, ASCT still remains only curative therapeutic modality for CLL, especially in countries with limited access to novel agents. Thirty patients with CLL at median age of 42 years at diagnosis (range 29-64) underwent ASCT between years 2002 and 2018. Thirteen patients were transplanted in complete remission (CR), ten patients achieved partial response (PR), and seven had stable disease. The median time from diagnosis to transplant was 4 years (range 0.5-12). Twenty-three patients received HLA-matched related donor stem cell grafts, and seven patients received either matched unrelated donor or HLA-mismatched grafts. Reduced intensity conditioning (RIC) and myeloablative regimen (MAC) were used in 24 and 6 patients, respectively. Mortality to day + 100 after transplant was 16% (8% for RIC only). Acute and chronic graft versus host disease (GVHD) developed in 40% and 63% of patients, respectively. Fifteen patients relapsed or progressed after transplant. Thirteen patients (43%) are alive at last follow-up and 10 (77%) remain in clinical CR. Median follow-up for survivors was 6.8 years (range 0.4-15.2). Three-year progression-free and overall survivals were 56% and 60%, respectively. These outcomes were better for patients who received RIC conditioning: 64% and 72%, respectively. CR at transplant was found to have favorable impact on post-allograft survival. RIC should be preferred over MAC. ASCT may remain a valuable option for some CLL patients.

Minimal residual disease in chronic lymphocytic leukemia: A consensus paper that presents the clinical impact of the presently available laboratory approaches

Chronic lymphocytic leukemia (CLL) is a malignancy defined by the accumulation of mature lymphocytes in the lymphoid tissues, bone marrow, and blood. Therapy for CLL is guided according to the Rai and Binet staging systems. Nevertheless, state-of-the-art protocols in disease monitoring, diagnostics, and prognostics for CLL are based on the assessment of minimal residual disease (MRD). MRD is internationally considered to be the level of disease that can be detected by sensitive techniques and represents incomplete treatment and a probability of disease relapse. MRD detection has been continuously improved by the quick development of both flow cytometry and molecular biology technology, as well as by next-generation sequencing. Considering that MRD detection is moving more and more from research to clinical practice, where it can be an independent prognostic marker, in this paper, we present the methodologies by which MRD is evaluated, from translational research to clinical practice.

A Novel Natural Product, KL-21, Inhibits Proliferation and Induces Apoptosis in Chronic Lymphocytic Leukemia Cells

Objective:

The aims of this study were to examine the cytotoxic and apoptotic effects of KL-21, a novel plant product (produced by Naturin Natural Products, İzmir, Turkey), on 232B4 chronic lymphocytic leukemia (CLL) cells and to determine the cytotoxic effects on healthy BEAS-2B human bronchial epithelial cells.

Materials and Methods:

The cytotoxic effect of KL-21 was determined by MTT cell proliferation assay. Changes in caspase-3 enzyme activity were measured using the caspase-3 colorimetric assay. Changes in mitochondrial membrane potential were determined using the JC-1 dye-based method. Annexin V-FITC/PI double staining was performed to measure the apoptotic cell population. Effects of KL-21 on cell cycle profiles of CLL cells were investigated by flow cytometry.

Results:

We detected time- and concentration-dependent increases in the cytotoxic effect of KL-21 on 232B4 CLL cells. However, we also showed that, especially at higher concentrations, KL-21 was less cytotoxic towards BEAS-2B healthy cells than towards CLL cells. Annexin-V/PI double staining results showed that the apoptotic cell population increased in 232B4 cells. Increasing concentrations of KL-21 increased caspase-3 enzyme activity and induced loss of mitochondrial membrane potential. KL-21 administration resulted in small increases in the percentage of the cells in the G0/G1 phase while it decreased the S phase cell population up to 1 mg/mL. At the highest concentration, most of the cells accumulated in the G0/G1 phase.

Conclusion:

KL-21 has a growth-inhibitory effect on 232B4 CLL cells. KL-21 causes apoptosis and cell cycle arrest at G0/G1.

Milestones of Hematopoietic Stem Cell Transplantation - From First Human Studies to Current Developments

Since the early beginnings, in the 1950s, hematopoietic stem cell transplantation (HSCT) has become an established curative treatment for an increasing number of patients with life-threatening hematological, oncological, hereditary, and immunological diseases. This has become possible due to worldwide efforts of preclinical and clinical research focusing on issues of transplant immunology, reduction of transplant-associated morbidity, and mortality and efficient malignant disease eradication. The latter has been accomplished by potent graft-versus-leukemia (GvL) effector cells contained in the stem cell graft. Exciting insights into the genetics of the human leukocyte antigen (HLA) system allowed improved donor selection, including HLA-identical related and unrelated donors. Besides bone marrow, other stem cell sources like granulocyte-colony stimulating-mobilized peripheral blood stem cells and cord blood stem cells have been established in clinical routine. Use of reduced-intensity or non-myeloablative conditioning regimens has been associated with a marked reduction of non-hematological toxicities and eventually, non-relapse mortality allowing older patients and individuals with comorbidities to undergo allogeneic HSCT and to benefit from GvL or antitumor effects. Whereas in the early years, malignant disease eradication by high-dose chemotherapy or radiotherapy was the ultimate goal; nowadays, allogeneic HSCT has been recognized as cellular immunotherapy relying prominently on immune mechanisms and to a lesser extent on non-specific direct cellular toxicity. This chapter will summarize the key milestones of HSCT and introduce current developments.

Paradigm shifts in the management of poor-risk chronic lymphocytic leukemia

With the growing complexity of treatment options for chronic lymphocytic leukemia (CLL) and variables that influence the underlying biology of this disease, providing allogeneic stem cell transplant (alloSCT) to appropriate candidates poses a challenge for transplant physicians. Novel small molecule inhibitors hold unprecedented promise for poor-risk subgroups, which will likely alter decision-making and referral patterns for transplant. In this review, we analyze what is known and may still remain true about indications for transplant based on outcomes reported in the literature recently and over the last decade.

Outcomes of human leukocyte antigen-matched sibling donor hematopoietic cell transplantation in chronic lymphocytic leukemia: myeloablative versus reduced-intensity conditioning regimens

Allogeneic hematopoietic cell transplantation (HCT) can cure some chronic lymphocytic leukemia (CLL) subjects. This study compared outcomes of myeloablative (MA) and reduced-intensity conditioning (RIC) transplants from HLA-matched sibling donors (MSD) for CLL. From 1995 to 2007, information regarding 297 CLL subjects was reported to the Center of International Blood and Marrow Transplant Research; of these, 163 underwent MA and 134 underwent RIC MSD HCT. The MA subjects underwent transplantation less often after 2000 and less commonly received antithymocyte globulin (4% versus 13%, P = .004) or prior antibody therapy (14% versus 53%; P < .001). RIC was associated with a greater likelihood of platelet recovery and less grade 2 to 4 acute graft-versus-host disease compared with MA conditioning. One- and 5-year treatment-related mortality (TRM) were 24% (95% confidence intervals [CI], 16% to 33%) versus 37% (95% CI, 30% to 45%; P = .023), and 40% (95% CI, 29% to 51%) versus 54% (95% CI, 46% to 62%; P = .036), respectively, and the relapse/progression rates at 1 and 5 years were 21% (95% CI, 14% to 29%) versus 10% (95% CI, 6% to 15%; P = .020), and 35% (95% CI, 26% to 46%) versus 17% (95% CI, 12% to 24%; P = .003), respectively. MA conditioning was associated with better progression-free (PFS) (relative risk, .60; 95% CI, .37 to .97; P = .038) and 3-year survival in transplantations before 2001, but for subsequent years, RIC was associated with better PFS and survival (relative risk, 1.49 [95% CI, .92 to 2.42]; P = .10; and relative risk, 1.86 [95% CI, 1.11 to 3.13]; P = .019). Pretransplantation disease status was the most important predictor of relapse (P = .003) and PFS (P = .0007) for both forms of transplantation conditioning. MA and RIC MSD transplantations are effective for CLL. Future strategies to decrease TRM and reduce relapses are warranted.

The prognostic impact of minimal residual disease in patients with chronic lymphocytic leukemia requiring first-line therapy

A proportion of patients with chronic lymphocytic leukemia achieve a minimal residual disease negative status after therapy. We retrospectively evaluated the impact of minimal residual disease on the outcome of 255 consecutive patients receiving any front-line therapy in the context of a detailed prognostic evaluation, including assessment of IGHV, TP53, NOTCH1 and SF3B1 mutations. The median follow-up was 73 months (range, 2-202) from disease evaluation. The median treatment-free survival durations for patients achieving a complete response without or with minimal residual disease, a partial response and no response were 76, 40, 11 and 11 months, respectively (P<0.001). Multivariate analysis revealed that three variables had a significant impact on treatment-free survival: minimal residual disease (P<0.001), IGHV status (P<0.001) and β2-microglobulin levels (P=0.012). With regards to overall survival, factors predictive of an unfavorable outcome were minimal residual disease positivity (P=0.014), together with advanced age (P<0.001), unmutated IGHV status (P=0.001), TP53 mutations (P<0.001) and elevated levels of β2-microglobulin (P=0.003). In conclusion, for patients requiring front-line therapy, achievement of minimal residual disease negativity is associated with significantly prolonged treatment-free and overall survival irrespective of other prognostic markers or treatment administered.

New approaches to manipulate minimal residual disease after allogeneic stem cell transplantation

Minimal residual disease (MRD) is a complex topic that has been studied extensively in hematologic malignancies given its clinical implications related to prognosis. However, methods to monitor and treat MRD, especially after stem cell transplantation, are not well defined and vary in different disease processes. Alternative transplant strategies, such as reduced-intensity conditioning, have altered the way we assess and address MRD after transplantation. Development of new diagnostic tools have allowed for higher sensitivity and specificity of testing. Both targeted chemotherapeutic agents and immunotherapies have been developed to treat MRD in hopes of improving patient outcomes. This article aims to address ways to define and manipulate MRD specifically after stem cell transplantation.

Rituximab maintenance after first-line therapy with rituximab, fludarabine, cyclophosphamide, and mitoxantrone (R-FCM) for chronic lymphocytic leukemia

The effectiveness of rituximab maintenance therapy in the treatment of chronic lymphocytic leukemia has been investigated in a phase 2 clinical trial that included an initial treatment with rituximab 500 mg/m2 on day 1 (375 mg/m2 the first cycle), fludarabine 25 mg/m2 on days 1 to 3, cyclophosphamide 200 mg/m2 on days 1 to 3, and mitoxantrone 6 mg/m2 on day 1 (R-FCM), for 6 cycles, followed by a maintenance phase with rituximab 375 mg/m2 every 3 months for 2 years. Sixty-seven patients having achieved complete response (CR) or partial response (PR) with R-FCM were given maintenance therapy. At the end of maintenance, 40.6% of patients were in CR with negative minimal residual disease (MRD), 40.6% were in CR MRD-positive, 4.8% remained in PR, and 14% were considered failures. Six of 29 patients (21%) who were in CR MRD-positive or in PR after R-FCM improved their response upon rituximab maintenance. The 4-year progression-free survival (PFS) and overall survival rates were 74.8% and 93.7%, respectively. MRD status after R-FCM induction was the strongest predictor of PFS. Maintenance with rituximab after R-FCM improved the quality of the response, particularly in patients MRD-positive after initial treatment, and obtained a prolonged PFS. This trial was registered at www.clinicaltrialsregister.eu as identifier #2005-001569-33.

Indications and outcomes of reduced-toxicity hematopoietic stem cell transplantation in adult patients with hematological malignancies

Hematopoietic stem cell transplantation (HCT) utilizing non-myeloablative (NMA) and reduced-intensity conditioning (RIC) regimens (collectively referred to as reduced-toxicity HCT, RT-HCT) has become a viable therapeutic option for patients with hematological malignancies who are ineligible for standard myeloablative conditioning transplantation (MA-HCT). RT-HCT has been shown to induce stable engraftment with low toxicity, and to produce similar overall and progression-free survival (PFS) when compared to MA-HCT in acute myeloid leukemia and myelodysplastic syndrome. The best results for RT-HCT have been reported for patients with disease that is in remission, indolent and chemosensitive, and with a strong graft-versus-malignancy effect. Chronic graft-versus-host disease seems to correlate with a lower relapse rate and better PFS. RT-HCT is inferior when performed in poor risk or advanced disease, due to high relapse rates. A search for novel strategies that includes the most appropriate conditioning regimens and post-transplant immunomodulation protocols with more intensive anti-malignancy activity but limited toxicity is in progress. This review provides an update on the results of clinical studies of RT-HCT, and discusses possible indications and investigative strategies for improving the clinical outcomes of RT-HCT for the major hematological malignancies.

A look into the future: can minimal residual disease guide therapy and predict prognosis in chronic lymphocytic leukemia?

Over the past 2 decades, dramatic improvements in the efficacy of treatments for chronic lymphocytic leukemia have led to progressively higher percentages of clinical complete remissions. A molecular eradication of the leukemia has become not only a desirable, but also an achievable, end point that needs to be evaluated within clinical trials. The assessment of complete remission only at the clinical and morphological level is insufficient, at least for physically fit patients. The detection of minimal residual disease (MRD) in chronic lymphocytic leukemia has become feasible using PCR-based or flow cytometric techniques that reproducibly allow reaching the detection level of less than 1 leukemic cell per 10 000 leukocytes (10−4), the level currently defined as MRD− status. Emerging data indicate that the MRD status during and at the end of treatment is one of the most powerful predictors of progression-free and overall survival. This predictor appears to be independent of clinical response, type or line of therapy, and known biological markers. For these reasons, the time is ripe to test the use of MRD as a surrogate marker of clinical end points and as a real-time marker of efficacy and/or resistance to the administered therapies. In the near future, clinical trials will determine whether MRD assessment can be used for guiding therapy, either to improve quality of responses through consolidation or to prevent relapses through preemptive therapies based on the reappearance of MRD.

Early autologous stem cell transplantation for chronic lymphocytic leukemia: long-term follow-up of the German CLL Study Group CLL3 trial

The CLL3 trial was designed to study intensive treatment including autologous stem cell transplantation (autoSCT) as part of first-line therapy in patients with chronic lymphocytic leukemia (CLL). Here, we present the long-term outcome of the trial with particular focus on the impact of genomic risk factors, and we provide a retrospective comparison with patients from the fludarabine-cyclophosphamide-rituximab (FCR) arm of the German CLL Study Group (GCLLSG) CLL8 trial. After a median observation time of 8.7 years (0.3-12.3 years), median progression-free survival (PFS), time to retreatment, and overall survival (OS) of 169 evaluable patients, including 38 patients who did not proceed to autoSCT, was 5.7, 7.3, and 11.3 years, respectively. PFS and OS were significantly reduced in the presence of 17p- and of an unfavorable immunoglobulin heavy variable chain mutational status, but not of 11q-. Five-year nonrelapse mortality was 6.5%. When 110 CLL3 patients were compared with 126 matched patients from the FCR arm of the CLL8 trial, 4-year time to retreatment (75% vs 77%) and OS (86% vs 90%) was similar despite a significant benefit for autoSCT in terms of PFS. In summary, early treatment intensification including autoSCT can provide very effective disease control in poor-risk CLL, although its clinical benefit in the FCR era remains uncertain. The trial has been registered with www.clinicaltrials.gov as NCT00275015.

High-throughput VDJ sequencing for quantification of minimal residual disease in chronic lymphocytic leukemia and immune reconstitution assessment

The primary cause of poor outcome following allogeneic hematopoietic cell transplantation (HCT) for chronic lymphocytic leukemia (CLL) is disease recurrence. Detection of increasing minimal residual disease (MRD) following HCT may permit early intervention to prevent clinical relapse; however, MRD quantification remains an uncommon diagnostic test because of logistical and financial barriers to widespread use. Here we describe a method for quantifying CLL MRD using widely available consensus primers for amplification of all Ig heavy chain (IGH) genes in a mixture of peripheral blood mononuclear cells, followed by high-throughput sequencing (HTS) for disease-specific IGH sequence quantification. To achieve accurate MRD quantification, we developed a systematic bioinformatic methodology to aggregate cancer clone sequence variants arising from systematic and random artifacts occurring during IGH-HTS. We then compared the sensitivity of IGH-HTS, flow cytometry, and allele-specific oligonucleotide PCR for MRD quantification in 28 samples collected from 6 CLL patients following allogeneic HCT. Using amplimer libraries generated with consensus primers from patient blood samples, we demonstrate the sensitivity of IGH-HTS with 454 pyrosequencing to be 10(-5), with a high correlation between quantification by allele-specific oligonucleotide PCR and IGH-HTS (r = 0.85). From the same dataset used to quantify MRD, IGH-HTS also allowed us to profile IGH repertoire reconstitution after HCT-information not provided by the other MRD methods. IGH-HTS using consensus primers will broaden the availability of MRD quantification in CLL and other B cell malignancies, and this approach has potential for quantitative evaluation of immune diversification following transplant and nontransplant therapies.

Autologous hematopoietic stem cell transplantation in chronic lymphocytic leukemia: results of European intergroup randomized trial comparing autografting versus observation

We present results of a phase 3 randomized trial of autografting in chronic lymphocytic leukemia versus observation for responding patients after first- or second-line treatment. The primary objective was to demonstrate that autografting improves the 5-year event-free survival (EFS) from 30% to 50%. There were 223 enrolled patients, 72% men and 28% women, 83% after first and 17% after second-line treatment. Binet stages were progressive A 13%, B 67%, C 20%; at randomization, 59% were in complete remission, and 41% in less than complete remission. Patients were randomized between autografting (n = 112) and observation (n = 111). Median EFS was 24.4 months (range, 16.7-32 months) in the observation group and 51.2 months (39.8-62.5 months) in the autografting group; the 5-year EFS was 24% and 42%, respectively (P < .001). Accordingly, the 5-year relapse incidence was 76% versus 54% (P < .001). Median time to relapse requiring therapy or death was 40 months (25-56 months) in the observation arm and 65 months (59-71 months) after autografting (P = .002). Cox modeling confirmed that autografting significantly improved EFS (hazard ratio 0.44, 95% confidence interval 0.30-0.65; P < .001). At 5 years, the probability of OS was 85.5% and 84.3% for autografting and observation, respectively (P = .77). In chronic lymphocytic leukemia, consolidating autografting reduces the risk of progression by more than 50% but has no effect on overall survival.

Stem cell transplantation in chronic lymphocytic leukaemia - steering a safe course over shifting sands

There is no clear consensus regarding the optimal management of chronic lymphocytic leukaemia. Many patients are diagnosed at an advanced age and will die with chronic lymphocytic leukaemia, but of other unrelated causes. A significant minority are diagnosed at an earlier age, or with more aggressive disease, and despite chemotherapy, are likely to die of chronic lymphocytic leukaemia. The infusion of autologous or allogeneic haemopoietic stem cells, following a variety of conditioning regimes, offers the possibility of longer remissions or even cure. We explore the key questions facing clinicians in this field: Who is it best to transplant? When is it best to transplant? How is it best to transplant?

The impact of HLA matching on long-term transplant outcome after allogeneic hematopoietic stem cell transplantation for CLL: a retrospective study from the EBMT registry

We analyzed 368 chronic lymphocytic leukemia patients who underwent allogeneic hematopoietic stem cell transplantation reported to the EBMT registry between 1995 and 2007. There were 198 human leukocyte antigen (HLA)-identical siblings; among unrelated transplants, 31 were well matched in high resolution ('well matched' unrelated donor, WMUD), and 139 were mismatched (MM), including 30 matched in low resolution; 266 patients (72%) received reduced-intensity conditioning and 102 (28%) received standard. According to the EBMT risk score, 11% were in scores 1-3, 23% in score 4, 40% in score 5, 22% in score 6 and 4% in score 7. There was no difference in overall survival (OS) at 5 years between HLA-identical siblings (55% (48-64)) and WMUD (59% (41-84)), P=0.82. In contrast, OS was significantly worse for MM (37% (29-48) P=0.005) due to a significant excess of transplant-related mortality. Also OS worsened significantly when EBMT risk score increased. HLA matching had no significant impact on relapse (siblings: 24% (21-27); WMUD: 35% (26-44), P=0.11 and MM: 21% (18-24), P=0.81); alemtuzumab T-cell depletion and stem cell source (peripheral blood) were associated with an increased risk. Our findings support the use of WMUD as equivalent alternative to HLA-matched sibling donors for allogeneic HSCT in CLL, and justify the application of EBMT risk score in this disease.

Efficacy of rituximab and cladribine in patients with chronic lymphocytic leukemia and feasibility of stem cell mobilization: a prospective multicenter phase II trial (protocol SAKK 34/02)

This phase II trial investigated rituximab and cladribine in chronic lymphocytic leukemia. Four induction cycles, comprising cladribine (0.1 mg/kg/day days 1-5, cycles 1-4) and rituximab (375 mg/m(2) day 1, cycles 2-4), were given every 28 days. Stem cell mobilization (rituximab 375 mg/m(2) days 1 and 8; cyclophosphamide 4 g/m(2) day 2; and granulocyte colony-stimulating factor 10 microg/kg/day, from day 4) was performed in responders. Of 42 patients, nine achieved complete remission (CR), 15 very good partial remission, and two nodular partial remission (overall response rate 62%). Stem cell mobilization and harvesting (> or = 2 x 10(6) stem cells/kg body weight) were successful in 12 of 20 patients. Rituximab infusion-related adverse events were moderate. The main grade 3/4 adverse events during induction were neutropenia and lymphocytopenia. Rituximab plus cladribine was effective; however, the CR rate was modest and stem cell harvest was impaired in a large number of responding patients.

Eradicating minimal residual disease in chronic lymphocytic leukemia: should this be the goal of treatment?

Even though chronic lymphocytic leukemia (CLL) is the most prevalent leukemia of the Western world, the development of treatment approaches for CLL has lagged behind the development of approaches to various other hematologic malignancies for a variety of reasons. In recent years, the treatment approach to patients with CLL has evolved rapidly, with the addition of several new prognostic markers, highly effective immunochemotherapy combinations, and attainment of remission up to the point of the eradication of minimal residual disease (MRD). Highly sensitive methods now available to detect MRD can detect a single CLL cell in 10(4) leukocytes using either allele-specific oligonucleotide polymerase chain reaction or four-color or six-color flow cytometry. Over the past decade, several studies have examined the possible advantage of MRD eradication in CLL. This article reviews our current understanding of MRD eradication and analyzes whether it is a desirable goal in the routine clinical treatment of CLL, which will optimize the management of individual patients.

Serologic markers of effective tumor immunity against chronic lymphocytic leukemia include nonmutated B-cell antigens

Patients with chronic lymphocytic leukemia (CLL) who relapse after allogeneic transplant may achieve durable remission following donor lymphocyte infusion (DLI), showing the potency of donor-derived immunity in eradicating tumors. We sought to elucidate the antigenic basis of the effective graft-versus-leukemia (GvL) responses associated with DLI for the treatment of CLL by analyzing the specificity of plasma antibody responses developing in two DLI-treated patients who achieved long-term remission without graft-versus-host disease. By probing high-density protein microarrays with patient plasma, we discovered 35 predominantly intracellular antigens that elicited high-titer antibody reactivity greater in post-DLI than in pre-DLI plasma. Three antigens-C6orf130, MDS032, and ZFYVE19-were identified by both patients. Along with additional candidate antigens DAPK3, SERBP1, and OGFOD1, these proteins showed higher transcript and protein expression in B cells and CLL cells compared with normal peripheral blood mononuclear cells. DAPK3 and the shared antigens do not represent minor histocompatibility antigens, as their sequences are identical in both donor and tumor. Although ZFYVE19, DAPK3, and OGFOD1 elicited minimal antibody reactivity in 12 normal subjects and 12 chemotherapy-treated CLL patients, 5 of 12 CLL patients with clinical GvL responses were serologically reactive to these antigens. Moreover, antibody reactivity against these antigens was temporally correlated with clinical disease regression. These B-cell antigens represent promising biomarkers of effective anti-CLL immunity.

High mitochondrial DNA stability in B-cell chronic lymphocytic leukemia

BACKGROUND

Chronic Lymphocytic Leukemia (CLL) leads to progressive accumulation of lymphocytes in the blood, bone marrow, and lymphatic tissues. Previous findings have suggested that the mtDNA could play an important role in CLL.

METHODOLOGY/PRINCIPAL FINDINGS

The mitochondrial DNA (mtDNA) control-region was analyzed in lymphocyte cell DNA extracts and compared with their granulocyte counterpart extract of 146 patients suffering from B-Cell CLL; B-CLL (all recruited from the Basque country). Major efforts were undertaken to rule out methodological artefacts that would render a high false positive rate for mtDNA instabilities and thus lead to erroneous interpretation of sequence instabilities. Only twenty instabilities were finally confirmed, most of them affecting the homopolymeric stretch located in the second hypervariable segment (HVS-II) around position 310, which is well known to constitute an extreme mutational hotspot of length polymorphism, as these mutations are frequently observed in the general human population. A critical revision of the findings in previous studies indicates a lack of proper methodological standards, which eventually led to an overinterpretation of the role of the mtDNA in CLL tumorigenesis.

CONCLUSIONS/SIGNIFICANCE

Our results suggest that mtDNA instability is not the primary causal factor in B-CLL. A secondary role of mtDNA mutations cannot be fully ruled out under the hypothesis that the progressive accumulation of mtDNA instabilities could finally contribute to the tumoral process. Recommendations are given that would help to minimize erroneous interpretation of sequencing results in mtDNA studies in tumorigenesis.

Allogeneic hematopoietic cell transplantation for chronic lymphocytic leukemia: ready for prime time?

The development of reduced intensity conditioning regimens has increased the number of patients diagnosed with chronic lymphocytic leukemia that are referred for allogeneic hematopoietic cell transplantation (allo-HCT). However, given the toxicity of allo-HCT, it should only be offered to eligible patients whose life expectancy is significantly reduced by the disease. Accordingly, the European Group of Blood and Marrow Transplantation has recently identified those patients in whom allo-HCT could be a reasonable therapeutic approach. In this review, we have evaluated the outcome of chronic lymphocytic leukemia patients undergoing allo-HCT, either after conventional or reduced intensity conditioning regimens, in the context of current nontransplantation strategies. We have also analyzed the most important predisposing factors that might interfere with the procedure as well as posttransplantation complications that are particularly common in these patients. Finally, we have addressed the most relevant factors when deciding what patients should be considered for allo-HCT and the timing of the procedure.

The role of stem cell transplantation in the management of chronic lymphocytic leukaemia

The majority of patients diagnosed with chronic lymphocytic leukaemia (CLL) will ultimately die of their disease. Stem cell transplantation (SCT) remains the only treatment modality capable of cure, but has traditionally been associated with very high morbidity and mortality. We review the results of myeloablative autologous and allogeneic SCT in CLL, discuss the evolution of the new non-myeloablative approaches, and make recommendations for when SCT should be considered in patients with CLL.

Qualitative and quantitative polymerase chain reaction monitoring of minimal residual disease in relapsed chronic lymphocytic leukemia: early assessment can predict long-term outcome after reduced intensity allogeneic transplantation

BACKGROUND

The graft-versus-leukemia effect is able to induce clinical responses in patients with chronic lymphocytic leukemia treated with a reduced intensity conditioning regimen, followed by allogeneic stem cell transplantation. We investigated whether molecular remissions could be attained after reduced intensity conditioning and allogeneic stem cell transplantation in patients with relapsed chronic lymphocytic leukemia and whether the assessment of minimal residual disease might be used to predict the clinical outcome.

DESIGN AND METHODS

Minimal residual disease was monitored by polymerase chain reaction using the immunoglobulin heavy-chain gene rearrangement as a molecular marker in 29 relapsed patients who achieved complete remission following reduced intensity conditioning and allogeneic stem cell transplantation. A nested-polymerase chain reaction with patient-specific primers derived from complementarity determining regions (CDR2 and CDR3) was carried out in all the patients. Real-time polymerase chain reaction was performed in patients whose nested reaction gave positive or mixed results.

RESULTS

Three patterns of minimal residual disease were observed: negative (31%), mixed (24%), and always positive (45%). The cumulative incidence of relapse according to the minimal residual disease status at 6 and 12 months after transplantation was significantly different between polymerase chain reaction-negative and -positive patients (p=0.031 and p=0.04, respectively). Two-year disease-free survival was 93% and 46% for polymerase chain reaction-negative and -positive patients at 6 months after transplantation, respectively (p=0.012). Similarly, 2-year disease-free survival was 100% and 57% for polymerase chain reaction-negative and -positive patients at 12 months, respectively (p=0.037). No clinical or biological factors were predictive of the achievement of polymerase chain reaction negativity after allogeneic stem cell transplantation. Graft-versus-host disease was more frequent in patients who did not relapse (p=0.04). Quantitative monitoring of minimal residual disease was able to identify polymerase chain reaction-positive patients with a higher risk of relapse.

CONCLUSIONS

These findings demonstrate that relapsed patients can achieve molecular remission after reduced intensity conditioning and allogeneic stem cell transplantation and suggest a minimal residual disease-driven intervention that might be useful to prevent overt hematologic relapse.

Monoclonal B-cell lymphocytosis

The incidence and presenting features of chronic lymphocytic leukemia (CLL) have changed significantly over the last century. Routine diagnostic techniques can now detect very low levels of CLL phenotype cells. Monoclonal B-cell lymphocytosis (MBL) is a relatively recent diagnostic category encapsulating individuals with an abnormal B-cell population but not meeting the diagnostic criteria for a B-cell malignancy. This review focuses on CLL-type MBL, which represents the majority of MBL cases identified in diagnostic laboratories. CLL-type MBL has a phenotype identical to CLL and shares the same chromosomal abnormalities even at the lowest levels detectable. Recent evidence suggests that the immunoglobulin gene usage plays a key role in whether the abnormal cells will develop in significant numbers. In most cases, CLL-type MBL is a stable condition with only 1% per year among those presenting for clinical attention developing progressive disease requiring treatment, although suppressed immune function may have a more significant impact on outcome.

Fludarabine, cyclophosphamide, and mitoxantrone as initial therapy of chronic lymphocytic leukemia: high response rate and disease eradication

PURPOSE

Fludarabine, cyclophosphamide, and mitoxantrone (FCM) results in a high response rate in previously treated patients with chronic lymphocytic leukemia (CLL). The aim of this study was to investigate FCM as frontline therapy in CLL.

EXPERIMENTAL DESIGN

Sixty-nine patients under the age of 65 years with active CLL were treated. Patients received six cycles of fludarabine 25 mg/m(2) i.v. x 3 days, cyclophosphamide 200 mg/m(2) i.v. x 3 days, and mitoxantrone 6 mg/m(2) i.v. x 1 day. Treatment outcome was correlated with clinical and biological variables. The clinical significance of eradicating minimal residual disease (MRD) was also analyzed.

RESULTS

The overall response, MRD-negative complete response (CR), MRD-positive CR, nodular partial response (PR), and PR rates were 90%, 26%, 38%, 14%, and 12%, respectively. Severe (grades 3 or 4) neutropenia developed in 10% of the patients. Major and minor infections were reported in 1% and 8% of cases, respectively. Median response duration was 37 months. Patients with del(17p) failed to attain CR. Patients achieving MRD-negative CR had a longer response duration and overall survival than patients with an inferior response. Low serum lactate dehydrogenase levels, low ZAP-70 expression, and mutated IgV(H) genes predicted longer response duration. Finally, both low ZAP-70 and CD38 expression in leukemic cells correlated with MRD-negativity achievement.

CONCLUSION

FCM induces a high response rate, including MRD-negative CRs in untreated patients with active CLL. Treatment toxicity is acceptable. Both high ZAP-70 and increased CD38 expression predict failure to obtain MRD-negative response. Patients in whom MRD can be eradicated have longer response duration and overall survival than those with inferior response. These results indicate that FCM can be an ideal companion for chemoimmunotherapy of patients with CLL.

Minimal residual disease assessment in chronic lymphocytic leukaemia

The concept of minimal residual disease (MRD) eradication in chronic lymphocytic leukaemia (CLL) is a relatively new one, as conventional therapy with alkylating agents is relatively ineffective and responding patients almost always have a significant tumour burden remaining at the end of treatment. However, a variety of novel therapies is now yielding higher response rates, and responses of better quality are now routinely achieved. This progress in therapy has been paralleled by an improvement in laboratory assays, allowing detection of CLL cells to levels as low as ten CLL cells in a million leukocytes. In this chapter we briefly review the existing methods for MRD assessment, the clinical relevance of MRD eradication in CLL, and the therapies available to attain this endpoint.

Genetically identical twin transplantation for chronic lymphocytic leukemia

We identified 19 persons with B-cell chronic lymphocytic leukemia (CLL) who received genetically identical twin blood cell or bone marrow transplants after high-dose conditioning. Ten are alive (eight disease-free) with a median follow-up of 89 months (range, 31-171 months); 5-year relapse rate was 50% (95% confidence interval (CI), 26-73%). Estimated 5-year survival and disease-free survival were 61% (95% CI, 37-82%) and 45% (95% CI, 23-68%). In two of four patients tested at 12 and 21 months by polymerase chain reaction no evidence of residual CLL was detected post-transplant. In one recipient who relapsed at 6 years, molecular studies showed a different CLL clone from that detected pretransplant. This clone was subsequently identified in the donor suggesting transfer of occult leukemia at the time of transplant. Genetically identical twin transplants can result in long-term disease-free survival and molecular remissions, these data suggest the potential for CLL control in the absence of allogeneic graft-versus-leukemia effect. The case of leukemia transfer indicates the need for careful evaluation of donors prior to graft collection.

Molecular methods used for the detection of autologous graft contamination in lymphoid disorders

Intensified treatments aimed at maximal tumor reduction are an important therapeutic option for patients affected by B-cell malignancies. The possibility of obtaining a relevant number of clinical complete remissions after these treatments prompted the application of molecular techniques for the detection of extremely low numbers of residual malignant cells. These cells can be present either in the stem cell graft or, during the follow-up, in the bone marrow of patients attaining a clinical complete remission. The most sensitive and widely used techniques for minimal residual disease (MRD) assessment are those based on the PCR method. These methods allow the detection of autologous graft contamination and the identification of patients at high risk of disease recurrence by means of post-transplant MRD monitoring. In this setting, quantitative PCR assays can evaluate the kinetics of tumor clone growth in complete remission (CR) patients showing a persistence of PCR detectable tumor cells with standard qualitative methods.

Chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is the most common adult leukemia in the western world and is due to the accumulation of mature B lymphocytes in the peripheral blood, bone marrow and secondary lymphoid organs. The leukemic cells show a distinct phenotype, which is essential to reach the correct diagnosis. Despite the phenotypic homogeneity, the clinical outcome may be significantly different. Some patients have an indolent leukemia, with long survival while others experience an aggressive disease, with early and frequent need of treatment. At present, no chemotherapeutic regimens can be considered curative and all patients will die with (or because of) their disease. In recent years, research on CLL has led to important discoveries that help defining patients' prognosis at the moment of diagnosis. These prognostic factors, which are derived from the biological features of the leukemic lymphocytes, are now rapidly moved into the clinical arena. They are used to stratify patients in selected clinical trials to assess the value of early and more modern treatments, which are becoming available to hematologists.

Graft-versus-leukaemia effect after non-myeloablative haematopoietic transplantation can overcome the unfavourable expression of ZAP-70 in refractory chronic lymphocytic leukaemia

ZAP-70 (zeta-chain-associated protein 70 kDa) expression is associated with poor prognosis in patients with chronic lymphocytic leukaemia (CLL). This study evaluated the efficacy of non-myeloablative allogeneic stem cell transplantation in patients with advanced CLL and assessed the impact of ZAP-70 expression on the outcome. Thirty-nine sequential patients were included. All had previously been treated with fludarabine. All patients received a preparative regimen of fludarabine (30 mg/m(2)/d for 3 d), intravenous cyclophosphamide (750 mg/m(2)/d for 3 d), and high-dose rituximab. Immunohistochemical techniques on marrow biopsy samples were used to determine that ZAP-70 was expressed in 25 patients, whereas 13 other patients were ZAP-70 negative, and one was of indeterminate status. With a median follow-up time of 27 months, the estimated overall survival and current progression-free survival (CPFS) rates at 4 years were 48% and 44% respectively. Patients who were ZAP-70 positive had 56% survival, and their CPFS rate increased from 30% to 53% after a donor lymphocyte infusion. Multivariate analysis indicated that chemorefractory disease and mixed T cell chimerism at day 90, but not ZAP-70 positivity, were associated with the risk of disease progression after transplantation. These results demonstrate a potent graft-versus-leukaemia effect that can overcome the adverse prognostic effect of ZAP-70 expression.

Graft-versus-leukemia in chronic lymphocytic leukemia

Immune-mediated anti-leukemia effects, often termed graft-versus-leukemia (GvL), operate after bone marrow or blood cell transplants for acute lymphoblastic leukemia, acute myelogenous leukemia and chronic myelogenous leukemia. Sometimes the magnitude of this anti-leukemia effect exceeds that of high-dose anti-leukemia drugs and radiation and can result in leukemia cure. We analyzed leukemia relapse data after transplants for chronic lymphocytic leukemia (CLL) in this context. These data support the notion of a strong GvL effect in CLL. However, as most of these data are from studies of allotransplants, it is uncertain whether GvL operates in settings where the anti-leukemia effector cells and target CLL cells are genetically identical except for leukemia-related mutations. It is also uncertain whether GvL is distinct from GvHD. These potential limitations have important implications on whether immune therapy of CLL will work in non-allotransplant settings.

Minimal residual disease in chronic lymphocytic leukaemia: is it ready for primetime?

New therapeutic modalities have substantially improved response rates and outcomes in chronic lymphocytic leukaemia (CLL), yet the mindset remains that palliation is the only goal of therapy because the disease is considered incurable. Ultimately, all patients relapse despite achieving an initial response, as minimal residual disease (MRD) persisting after therapy eventually evolves into morphological and clinical recurrence. The emergence of immune-based combination therapies capable of inducing molecular remissions, the availability of highly sensitive assays that detect MRD, and emerging data showing a longer duration of response or longer survival in patients with no detectable disease, suggest that eradicating MRD may be a reasonable option for some patients. Moreover, novel biological prognostic markers have divided CLL into favourable and unfavourable subtypes, arguing in favour of defining different goals of therapy for different patients. Clinicians are increasingly challenged with the task of how best to incorporate MRD assessment into clinical practice, especially in an era when these novel prognostic factors exist. This review summarises the current understanding of MRD from a clinical standpoint, suggests that MRD eradication maybe a reasonable option for some patients, and argues in favour of designing large randomised studies to determine whether MRD-negative remission improves outcome.

Flow cytometric protein expression profiling as a systematic approach for developing disease-specific assays: identification of a chronic lymphocytic leukaemia-specific assay for use in rituximab-containing regimens

Depletion of disease below the levels detected by sensitive minimal residual disease (MRD) assays is associated with prolonged survival in chronic lymphocytic leukaemia (CLL). Flow cytometric MRD assays are now sufficiently sensitive and rapid to guide the duration of therapy in CLL, but generally rely on assessment of CD20 expression, which cannot be accurately measured during and after therapeutic approaches containing rituximab. The aim of this study was to use analytical software developed for microarray analysis to provide a systematic approach for MRD flow assay development. Samples from CLL patients (n=49), normal controls (n=21) and other B-lymphoproliferative disorders (n=12) were assessed with a panel of 66 antibodies. The DNA-Chip analysis program was used to identify discriminating antibodies, with hierarchical cluster analysis to identify complementary combinations. An iterative process was used: increasing numbers of patients were assessed with smaller, more targeted antibody panels until a highly specific combination (CD81/CD22/CD19/CD5) was identified. This combination was as sensitive and specific as previously reported assays and potentially applicable to blood and marrow samples from patients treated with current therapeutic approaches including rituximab. This approach to the identification of disease-specific antibody combinations for MRD analysis is readily applicable to a variety of haematological disorders.

Role of allogeneic transplantation in low-grade lymphoma and chronic lymphocytic leukemia

PURPOSE OF REVIEW

Indolent lymphoproliferative disorders are incurable with conventional chemotherapy. Exploring the potential of allogeneic transplantation to eradicate disease has therefore been of interest for some time. This review reports on recent developments in this field to evaluate the current status of stem cell transplantation in the management of these conditions.

RECENT FINDINGS

Most recent studies examine the application of reduced intensity regimens in follicular non-Hodgkin's lymphoma and chronic lymphocytic leukemia. Interest is particularly focused on assessing the potency of the allogeneic graft-versus-malignancy effect, whether achieved by T cells infused at the time of transplant, or by the administration of exogenous donor lymphocytes at relapse or progression following transplant. Furthermore, the discovery of molecular/genetic factors that permit identification of patients with poor prognosis chronic lymphocytic leukemia has led to interest in identifying whether the allogeneic effect can overcome the impact of these factors.

SUMMARY

Encouraging evidence is accumulating for the efficacy of reduced intensity transplantation in indolent lymphoproliferative disorders. Allogeneic graft-versus-malignancy effects can be demonstrated and durable responses to donor lymphocytes are being reported. More follow-up is required, however, before the curative potential of allogeneic transplantation can be assessed. The appropriate timing of transplant and the choice of regimen remains unclear.

Chronic lymphocytic leukemia: diagnosis and treatment

Traditionally, the goal of therapy in chronic lymphocytic leukemia (CLL) has been palliative, with first-line therapy using alkylating agents and/or involved field radiotherapy (depending on the stage of disease and sites of involvement) because of the older age of affected patients and the low rate of complete remissions (CRs) with no improvement in overall survival despite treatment. With increasing knowledge about the biology, molecular genetics, and prognostic factors of the disease, the philosophy of care for patients with CLL has evolved from palliation to aiming for a potential cure, especially in younger patients. Furthermore, multiple treatment options have emerged, including purine analogues, monoclonal antibodies, and potentially stem cell transplantation. These have been associated with higher frequencies of CRs and longer durations of responses compared to conventional chemotherapy. In addition, a subset of patients treated with chemoimmunotherapy can achieve durable CRs and molecular remissions. This may translate into improved disease-free survival and potentially a "cure." Because of the heterogeneous nature of CLL, new prognostic markers are currently being incorporated into clinical trials to determine their role in routine clinical practice. This review summarizes current therapeutic regimens that are being evaluated in patients with CLL and management of disease-related complications.

Clinical significance of minimal residual disease, as assessed by different techniques, after stem cell transplantation for chronic lymphocytic leukemia

We analyzed minimal residual disease (MRD) by consensus polymerase chain reaction (PCR), quantitative PCR (qPCR), and flow cytometry in 40 patients with chronic lymphocytic leukemia (CLL) who underwent stem cell transplantation; 97.4%, 89%, and 100% of the patients could be studied by consensus PCR, qPCR, and flow cytometry, respectively. Overall, 164 of 248 samples were negative for MRD by consensus PCR. Among those, CLL cells were detected by qPCR and by flow cytometry in 77 (47%) and 39 (23%) of the 164 samples, respectively. All 84 samples positive on PCR had detectable CLL cells by qPCR and flow cytometry. A good correlation was seen between MRD levels by flow cytometry and by qPCR (n = 254; r = 0.826; P < .001). Fifteen of 25 patients receiving autografts suffered a relapse, with increasing levels of MRD being observed before relapse in all of them. MRD detection within the first 6 months after autologous transplantation identified patients with a high relapse risk. In contrast, in allografted patients (n = 15) MRD did not correlate with outcome. In conclusion, quantitative methods to assess MRD (flow cytometry and qPCR) are more accurate than consensus PCR to predict clinical evolution. These results might be useful to investigate treatments aimed at preventing relapse in patients with CLL who have received an autograft.

Evidence for involvement of clonally expanded CD8+ T cells in anticancer immune responses in CLL patients following nonmyeloablative conditioning and hematopoietic cell transplantation

We have analyzed the clonotype composition of CD8+ T cells following nonmyeloablative (NMA) conditioning and hematopoietic cell transplantation (HCT), of patients with chronic lymphocytic leukemia (CLL). Consecutive analyses of blood samples taken up to 2 years following HCT, demonstrated that CD8+ T-cell clonality was highly dynamic in the early phases after HCT, but became more stable after 4-5 months. Moreover, donor lymphocyte infusion (DLI) given for disease progression in one of the patients led to establishment of recurrent as well as new T-cell clonotypes. This coincided with disease remission, strongly suggesting that these T cells were engaged with anti-CLL cytotoxicity. To examine the functional capacity of stable clonally expanded T cells after HCT, CD8+ T cells isolated post-transplant from the recipients were stimulated ex vivo with CLL cells and subsequently analyzed by FACS for surface expression of the marker for cytotoxic activity, CD107a. Stimulation with CLL cells indeed led to surface expression of CD107a, and clonotype analyses of sorted cells demonstrated that CD107a positive T cells were stably expanded following HCT. Our data suggest that clonally expanded CD8+ T-cell clones participate in the ongoing T-cell response against CLL cells following HCT with NMA conditioning.

Autologous and allogeneic stem cell transplantations for poor-risk chronic lymphocytic leukemia

We report here on the long-term follow-up on 162 patients with high-risk chronic lymphocytic leukemia (CLL) who have undergone hematopoietic stem cell transplantation (SCT) at a single center from 1989 to 1999. Twenty-five patients with human leukocyte antigen (HLA)-matched sibling donors underwent T-cell-depleted allogeneic SCT, and 137 patients without HLA-matched sibling donors underwent autologous SCT. The 100-day mortality was 4% for both groups, but later morbidity and mortality were negatively affected on outcome. Progression-free survival was significantly longer following autologous than allogeneic SCT, but there was no difference in overall survival and no difference in the cumulative incidence of disease recurrence or deaths without recurrence between the 2 groups. At a median follow-up of 6.5 years there is no evidence of a plateau of progression-free survival. The majority of patients treated with donor lymphocyte infusions after relapse responded, demonstrating a significant graft-versus-leukemia effect in CLL. From these findings we have altered our approach for patients with high-risk CLL and are currently exploring the role of related and unrelated allogeneic SCT following reduced-intensity conditioning regimens.