The role of stem cell transplant for lymphoma in 2017 (2017)

The risks and benefits of high dose therapy (HDT) and autologous stem cell transplantation (ASCT) or allogeneic stem cell transplant (alloSCT) must always be weighed against the outcome in any disease setting compared with standard therapy. This is a constantly changing risk benefit and in diseases such as chronic myeloid leukemia or chronic lymphocytic leukemia, the role of alloSCT has been displaced by successful treatment with the targeted therapies imatinib for chronic myeloid leukemia and ibrutinib, idelalisib, and venetoclax for chronic lymphocytic leukemia. No targeted therapies have yet displaced the use of SCT in lymphomas, and this modality maintains a major role in the treatment of relapsed disease. Similarly, comparative studies exploring the role of AlloSCT versus ASCT have suggested a higher risk of nonrelapse mortality, a lower probability of disease relapse, but often similar overall survival (OS) in relapsed or refractory non-Hodgkin lymphoma. Careful patient selection and usage of reduced intensity conditioning (RIC) AlloSCT may allow reduction in nonrelapse mortality. Criteria for optimal patient selection, timing of SCT and the use of ASCT versus AlloSCT remain clinical questions that are best evaluated within well conducted clinical trials and are reviewed here The indications for each of the major subtypes of lymphoma, diffuse large B cell lymphoma, follicular lymphoma, mantle cell lymphoma and T cell lymphoma are shown in Tables 1-4 respectively. Diffuse large B cell lymphoma (DLBCL) comprises multiple molecular and biological subtypes, and this results in a broad range of clinical outcomes. Standard front-line chemo-immunotherapy with R-CHOP can be curative in ~50% of patients. Transplantation has a major role, particularly for relapsed patients who are sensitive to relapse therapy and in this setting, HDT and ASCT have been shown to improve outcome in randomized clinical trials. The role of HDT and ASCT was first established in a randomized trial of 109 patients who responded to dexamethasone, high dose Ara-C and Cisplatin (DHAP) salvage chemotherapy who were randomized to receive further cycles of DHAP or HDT and ASCT.1 The HDT and ASCT group had improved event free and OS. Disease sensitivity to salvage chemotherapy and longer time from first remission to relapse are associated with improved outcome after ASCT. Patients who undergo ASCT when the disease is resistant to salvage chemotherapy have higher treatment-related mortality (TRM), and the probability of long term durable disease-free survival is less than 20%. Positron emission tomography (PET) is strongly recommended for pretreatment evaluation and for final response assessment and a negative PET scan following induction chemotherapy is associated with improved outcome. A positive PET scan at the end of induction chemotherapy identifies patients with primary refractory disease but HDT and ASCT remains an option for this group of patients. There is a move towards targeted therapies to increase this cure rate, for those subgroups of patients who have poorer outcome, notably activated B cell DLBCL, double-hit lymphoma (DHL) defined by the dual translocation of MYC and BCL2 genes, and dual protein-expressing lymphomas defined by the overexpression of MYC and BCL2 protein. Primary refractory disease is common in double hit lymphomas that exhibit rearrangements of MYC and BCL2 genes. However, in the absence of successful targeted therapies, it was reasonable to attempt to improve the outcome in these patients by escalating chemotherapy and this remains the focus of much clinical research. The role of HDT and ASCT as part of initial therapy remains highly contentious and has been tested in many randomized trials, and the results have been often contradictory. Four randomized trials have been presented using HDT and ASCT in the rituximab era and none have shown an OS advantage. A meta-analysis of 15 randomized trials including more than 3000 patients has been reported.2 Thirteen of these studies including more than 2000 patients showed that HDT and ACST was associated with higher complete remission (CR) rates, but there was no OS benefit for HDT and ASCT. High dose therapy with ASCT in first line is therefore not recommended outside of clinical trials. Allogeneic SCT (AlloSCT) has also been explored in DLBCL, and the use of reduced intensity conditioning regimens has opened up this approach for patients who have relapsed after prior ASCT. The use of alloSCT in place of ASCT for those with high risk features remains a clinical trial question. Unlike aggressive lymphomas, the use of HDT with ASCT in the treatment of follicular lymphomas (FL) has not yet been as fully established. The rational for considering transplantation is that the disease is incurable using standard approaches, young patients with FL will die of their disease, and promising results have been observed in a number of phase II studies. Detection of MRD has been a useful surrogate marker for tracking long-term progression-free survival (PFS) in patients examining the autologous stem cells or in serial samples after transplantation. A major concern relates to the risk of development of development of secondary myelodysplasia/acute myeloid leukemia. The European Bone Marrow Transplant Registry sponsored CUP study (conventional chemotherapy, unpurged, purged autograft) is the only prospective randomized trial to assess the role of autologous SCT in patients with relapsed FL.3 The results of the study suggest a PFS and OS advantage of ASCT over conventional chemotherapy, with 4 years OS of 46% for the chemotherapy arm, versus 71% for the unpurged, and 77% for the purged ASCT arms. However, it should be remembered that this study was closed early because of slow accrual with 140 of the planned 250 patients accrued and only 89 randomized. The role of HDT and ASCT in FL patients during first remission was also explored in a number of phase II trials, and in 3 phase III randomized trials.4-6 The German Lymphoma Study Group (GLSG) trial4 recruited 307 previously untreated patients up to 60 years of age and patients who responded after induction chemotherapy with 2 cycles of CHOP or mitoxantrone-chlorambucil-prednisone were randomized to autologous SCT or IFN-alpha maintenance. Among 240 evaluable patients, the 5-year PFS was 64.7% for ASCT, and 33.3% in the IFN-alpha arm (P < .0001). Acute toxicity was higher in the ASCT group, but early mortality was below 2.5% in both study arms. Longer follow-up is necessary to determine the effect of ASCT on OS. In the Groupe Ouest Est des Leucemies Aigues et des Maladies du Sang study, 172 newly diagnosed advanced FL patients were randomized either to cyclophosphamide, doxorubicin, teniposide, prednisone, CHVP, and IFN-alpha or to HDT followed by purged ASCT.5 Patients treated with HDT had a higher response rate than patients who received chemotherapy and IFN-alpha (81% versus 69%, P = .045) and a longer median PFS (not reached versus 45 months), but this did not translate into a better OS due to an excess of secondary malignancies after transplantation. A subgroup of patients with a significantly higher event-free survival rate ASCT could be identified using the follicular lymphoma international prognostic index (FLIPI). The GELF94 study enrolled 401 previously untreated advanced stage FL patients who were randomized to receive CHVP plus IFN-alpha compared with 4 courses of CHOP followed by HDT with total body irradiation (TBI) and ASCT and OR rates were similar in both groups (79% and 78% respectively) and 87% of eligible patients underwent ASCT. Intent-to-treat analysis after a median follow-up of 7.5 years showed no difference between the 2 arms for OS (P = .53) or PFS (P = .11). Long-term follow-up demonstrated no statistically significant benefit in favor of first-line ASCT in patients with FL, which the investigators conclude should be reserved for relapsed patients. A meta-analysis concluded that that high-dose therapy and ASCT does not improve OS in FL.7 In view of these results, ASCT should be used in first remission only in the setting of clinical trials. There is a trend towards increasing use of allogeneic SCT in the management of indolent lymphomas. In a report of the International Bone Marrow Transplant Registry, results after SCT are described for 904 patients with FL.8 Among these patients, 176 patients underwent allogeneic SCT, 131 patients underwent autologous SCT using purged stem cells and 597 using unpurged autologous stem cells. The TRM in these 3 groups was 30%, 14%, and 8%, respectively, disease recurrence occurred in 21%, 43%, and 58%, and 5 years overall survival was 51%, 62%, and 55%, respectively. The use of TBI containing regimens was associated with increased TRM but decreased risk of relapse. The use of allogeneic SCT was associated with increased TRM, but significantly lower risk of disease recurrence in keeping with a graft versus lymphoma effect in this disease. Trends suggest that outcomes are improving and this is highly likely to continue with the use of reduced intensity conditioning regimens that have become used increasingly since the time this registry data was collated. Long term PFS has been observed after allogeneic SCT even in patients with refractory FL.9 In 29 FL patients, 11 of whom had refractory disease, the nonrelapse mortality was 24% and there was a 23% incidence of relapse. The 5-year OS was 58% with 53% event-free survival. A group of patients with very poor outcome are those patients who have relapsed after previous autologous SCT. The treatment-related mortality following myeloablative alloSCT was 22% and the probability of disease progression was 52% at 3 years in a study from the International Bone Marrow Transplant Registry. The use of TBI conditioning regimens and achievement of CR at the time of allogeneic SCT were associated with improved outcome. The use of reduced intensity conditioning regimens appears to be associated with improved outcome. The outcome following reduced intensity conditioning transplant regimen incorporating T cell depletion using alemtuzumab immunosuppressive therapy has been reported for 81 patients with lymphoma including 41 with low grade, 37 with high/intermediate grade, and 10 patients with mantle-cell lymphoma (MCL), 31 of whom had relapsed following previous autologous SCT.10 Patients received a conditioning regimen consisting of alemtuzumab, fludarabine, and melphalan, and received short course cyclosporine as graft-versus-host disease (GVHD) prophylaxis. The use of this conditioning regimen was associated with a low incidence of GVHD, and the TRM was notably decreased in patients with low grade compared to higher grade histology. The 3 years progression-free survival was 65% for patients with low grade lymphoma, 50% for patients with MCL, and 34% for high grade lymphoma (P = .002). Donor lymphocyte infusion (DLI) was given to 36 patients, 21 for relapsed or persistent disease, and 15 for persistence of mixed chimerism. The use of DLI to treat relapse after alloSCT is solely dependent upon the existence of a graft versus lymphoma effect. In seven patients with FL and SLL who had relapsed after prior allogeneic SCT, six patients responded and with four the CRs were maintained for 43-89 months. The effectiveness of DLI to treat relapse after allogeneic SCT provides perhaps the strongest evidence for a graft versus lymphoma effect that can be exploited in indolent lymphomas. The role of RIC allogeneic SCT has been evaluated by Cancer and Leukemia Group B in a phase II study to evaluate the safety and efficacy in patients with recurrent low-grade B cell malignancies, including 16 patients with FL. The 3-year TRM was 9%, and the 3-year OS was 81%. The incidence of grade II-IV acute GVHD was 29%, and extensive chronic GVHD was 18%. Transformation of FL to high grade histology is associated with poor outcome and the role of SCT has been explored. A multicenter study of 172 patients with transformation of FL concluded that ASCT was associated with improved outcomes than those treated with chemotherapy alone, but this was not seen with AlloSCT because of the high TRM.11 Mantle-cell lymphoma is characterized by poor prognosis with a median survival historically of only 3 to 4 years, although this is improving with newer therapies. The European MCL Network initiated a randomized trial comparing consolidation with myeloablative radio-chemotherapy followed by ASCT to maintenance with alpha-interferon in first remission in 122 patients up to the age of 65 years of age or younger with advanced-stage MCL who achieved complete or partial remission after CHOP-like induction therapy.12 Sixty-two patients proceeded to ASCT and 60 received IFN alpha. Patients in the ASCT arm had a significantly longer PFS (median of 39 months compared with 17 months for patients in the IFN alpha arm P = .0108). However, the 3-year OS was only 83% after ASCT versus 77% in the IFN group (P = .18). They concluded that early consolidation by myeloablative radiochemotherapy followed by ASCT is feasible and results in a significant prolongation of PFS in advanced-stage MCL, but that longer follow-up is needed to determine the effect on OS. Following publication of this and other phase II studies suggesting improved outcome for ASCT in first remission, this approach has become standard in most centers. The role of ASCT in later lines of treatment remains much more controversial and alloSCT is more commonly offered. The role of alloSCT is less established, but its role is supported by a number of single center studies, usually using RIC alloSCT. The role of both ASCT and alloSCT remains to be clarified in MCL and has been reviewed recently by the EBMT/European MCL network who have published their guidelines.13 The panel concluded that ASCT is the standard of care for younger fitter patients in first remission. The role of alloSCT to consolidate first response, even in high-risk patients, is not yet established and is associated with significant toxicity and the panel did not support the use of alloSCT for first-line consolidation in such high-risk patients. A number of single-center prospective studies and retrospective registry studies have been reported with conflicting data regarding both toxicity and efficacy of RIC alloSCT with many of these patients having failed a previous ASCT. There was a partial consensus among the experts in support of alloSCT for relapse after ASCT. It was felt that the benefit of an RIC alloSCT in this setting will likely depend upon a number of factors notably the time from ASCT to relapse. Peripheral T-cell lymphoma (PTCL) comprises a heterogeneous group of mature T-cell tumors with a generally poor prognosis; ASCT and alloSCT offer a potential cure for these patients though the optimal type and timing of SCT remains to be defined. The Nordic Lymphoma Group (NLG) conducted the largest prospective phase II study in 160 untreated systemic PTCL patients to evaluate the efficacy of a dose-dense approach consolidated by up-front HDT and ASCT.14 The authors concluded that HDT and ASCT were well tolerated and led to long-term PFS in 44% of treatment-naive patients with PTCL. This represents an encouraging outcome, particularly considering the high median age and adverse risk profile of the study population. They concluded that HDT and ASCT are a rational up-front strategy in transplantation-eligible patients with PTCL. The role of ASCT has been less well-defined in relapsed disease although several retrospective studies have been published on the use of ASCT as salvage treatment. Taken together, the data from published studies show that the ASCT as salvage strategy appears feasible and safe with a low morbidity and mortality.15 As in other disease settings, the most important prognostic factor is the remission status of the patients at the time of ASCT, with better long-term survival in patients transplanted in CR, compared to patients with other disease status. It must be noted that all data in this setting are generated retrospectively and this requires further confirmation. Studies investigating the role of alloSCT as part of first-line therapy in poor-risk T-cell lymphomas are ongoing. Data are not yet sufficient to recommend alloSCT outside of clinical trials. Patients with relapsed or refractory anaplastic lymphoma kinase–negative anaplastic large cell lymphoma, angioimmunoblastic T-cell lymphoma (AITL), or peripheral T-cell lymphoma, not otherwise specified (PTCL-NOS) achieve long-term survival in 35%-50% of cases after alloSCT and survival in patients with less frequent subtypes also seems promising. These results appear significantly better than those of any other treatment modality, including the new drugs. Therefore, alloSCT should be considered in patients with relapsed/refractory T-cell lymphoma. Because of low patient numbers and lack of comparative studies, the optimum conditioning regimen prior to transplantation as well as other details of the transplant procedure remain unknown and require further study.16 Stem cell transplantation has an established role in the management of lymphomas. Randomized clinical trials showing a benefit for SCT must always be interpreted in light of advances in standard treatments since the time of publication of the studies. The role of SCT in rarer circumstances is often circumstantial and SCT and particularly the role of ASCT versus alloSCT must always be considered in the setting of the needs of an individual patient. Chemosensitivity to last treatment, duration of last response, and overall fitness for transplants appear the most important factors for consideration. Professor Gribben receives Research support from Janssen and Acerta, and support for clinical trial: Roche/Genentech, Takeda, Celgene, Pharmacyclics, Gilead, Abbvie, Janssen, Epizyme, Medimmune, and Merck. He has received honoraria from Roche/Genentech, Janssen, Pharmacyclics, Abbvie, TG Therapeutics, Celgene, and Epizyme and for providing scientific advice to Genentech, Abbvie, Unum, Cellectis, Pharmacyclics and Acerta.