Treatment
First-Line Therapy. DLBCL is an aggressive disease and, in most cases, survival without treatment can be measured in weeks to months. The advent of combination chemotherapy (CHOP [cyclophosphamide, doxorubicin, vincristine, and prednisone] or CHOP-like regimens) led to disease-free survival (DFS) rates of 35% to 40% at 3 to 5 years [33]. The addition of rituximab to CHOP (R-CHOP) has improved both progression-free surivial (PFS) and OS [34,35].
Treatment options vary for patients with localized (stage I/II) and advanced (stage III/IV) disease. Options for limited-stage DLBCL include an abbreviated course of R-CHOP (3 or 4 cycles) with involved-field radiation therapy (IFRT) versus a full course (6–8 cycles) of R-CHOP without radiation therapy (RT). Most studies comparing combined modality therapy (chemotherapy plus RT) versus chemotherapy alone were conducted in the pre-rituximab era. With the introduction of rituximab, Persky and colleagues [36] studied the use of 3 cycles of R-CHOP followed by RT, demonstrating a slightly improved OS of 92% at 4 years as compared to 88% in a historical cohort. The French LYSA/GOELAMS group performed the only direct comparison in the rituximab era (4 cycles of R-CHOP followed by RT versus 4 cycles of R-CHOP followed by 2 additional cycles of R-CHOP) and reported similar outcomes between both arms [37], with OS of 92% in the R-CHOP alone arm and 96% in the R-CHOP + RT arm (nonsignificant difference statistically). IFRT alone is not recommended other than for palliation in patients who cannot tolerate chemotherapy or combined modality therapy. Stage I and II patients with bulky disease (> 10 cm) have a prognosis similar to patients with advanced DLBCL and should be treated aggressively with 6 to 8 cycles of R-CHOP with or without RT [36].
For patients with advanced stage disease, a full course of R-CHOP-21 (6–8 cycles given on a 21-day cycle) is the standard of care. This approach results in OS rates of 70% and 60% at 2 and 5 years, respectively. For older adults unable to tolerate full-dose R-CHOP, attenuated versions of R-CHOP with decreased dose density or decreased dose intensity have been developed [38]. Numerous randomized trials have attempted to improve upon the results of R-CHOP-21 using strategies such as infusional chemotherapy (DA-EPOCH-R [etoposide, prednisone, vincristine, cyclophosphamide, doxorubicin, rituximab]) [39]; dose-dense therapy (R-CHOP-14); replacement of rituximab with obinutuzuimab [40]; addition of novel agents such as bortezomib [41], lenalidomide[42], or ibrutinib [43,44] to R-CHOP; and various maintenance strategies such as rituximab, lenalidomide [45], enzastaurin [46], and everolimus [47]. Unfortunately, none of these strategies has been shown to improve OS in DLBCL. In part this appears to be due to the fact that inclusion/exclusion criteria for DLBCL trials have been too strict, such that the most severely ill DLBCL patients are typically not included. As a result, the results in the control arms have ended up better than what was expected based on historical data. Efforts are underway to include all patients in future first-line DLBCL studies.
Currently, autologous hematopoietic cell transplantation (auto-HCT) is not routinely used in the initial treatment of DLBCL. In the pre-rituximab era, numerous trials were conducted in DLBCL patients with high and/or high-intermediate risk disease based on the IPI score to determine if outcomes could be improved with high-dose therapy and auto-HCT as consolidation after patients achieved complete remission with first-line therapy. The results of these trials were conflicting. A 2003 meta-analysis of 11 such trials concluded that the results were very heterogeneous and showed no OS benefit [48]. More recently, the Southwestern Oncology Group published the results of a prospective trial testing the impact of auto-HCT for consolidation of aggressive NHL patients with an IPI score of 3 to 5 who achieved complete remission with first-line therapy with CHOP or R-CHOP. In this study, 75% of the patients had DLBCL and, of the B-cell NHL patients, 47% received R-CHOP. A survival benefit was seen only in the subgroup that had an IPI score of 4 or 5; a subgroup analysis restricted to those receiving R-CHOP as induction was not performed, however [49]. As a result, this area remains controversial, with most institutions not routinely performing auto-HCT for any DLBCL patients in first complete remission and some institutions considering auto-HCT in first complete remission for patients with an IPI score of 4 or 5. These studies all used the IPI score to identify high-risk patients. It is possible that the use of newer biomarkers or minimal-residual disease analysis will lead to a more robust algorithm for identifying high-risk patients and selecting patients who might benefit from consolidation of first complete remission with auto-HCT.
For patients with DHL or THL, long-term PFS with standard R-CHOP therapy is poor (20% to 40%) [50,51]. Treatment with more intensive first-line regimens such as DA-EPOCH-R, R-hyperCVAD (rituximab plus hyperfractionated cyclophosphamide, vincristine, doxorubicin, dexamethasone), or CODOX-M/IVAC±R (cyclophosphamide, vincristine, doxorubicin, high‐dose methotrexate/ifosfamide, etoposide, high‐dose cytarabine ± rituximab), along with CNS prophylaxis, however, has been shown to produce superior outcomes [52], with 3-year relapse-free survival rates of 88% compared to 56% for R-CHOP. For patients who achieve a complete response by PET/CT scan after intensive induction, consolidation with auto-HCT has not been shown to improve outcomes based on retrospective analysis. However for DHL/THL patients who achieve complete response after R-CHOP, PFS was improved if auto-HCT was given as consolidation of first remission [53].
Patients with DLBCL have an approximately 5% risk of subsequently developing CNS involvement. Historically (in the pre-rituximab era), patients who presented with multiple sites of extranodal disease and/or extensive bone marrow involvement and/or an elevated LDH had an increased risk (up to 20%–30%) of developing CNS involvement. In addition, patients with involvement of certain anatomical sites (testicular, paranasal sinuses, epidural space) had an increased risk of CNS disease. Several algorithms have been proposed to identify patients who should receive prophylactic CNS therapy. One of the most robust tools for this purpose is the CNS-IPI, which is a 6-point score consisting of the 5 IPI elements, plus 1 additional point if the adrenal glands or kidneys are involved. Importantly, the CNS-IPI was developed and validated in patients treated with R-CHOP-like therapy. Subsequent risk of CNS relapse was 0.6%, 3.4%, and 10.2% for those with low-, intermediate- and high-risk CNS-IPI scores, respectively [54]. A reasonable strategy, therefore, is to perform CNS prophylaxis in those with a CNS-IPI score of 4 to 6. When CNS prophylaxis is used, intrathecal methotrexate or high-dose systemic methotrexate is most frequently given, with high-dose systemic methotrexate favored over intrathecal chemotherapy given that high-dose methotrexate penetrates the brain and spinal cord parenchyma, in addition to treating the cerebrospinal fluid (CSF) [55]. In contrast, intrathecal therapy only treats the CSF and requires repeated lumbar punctures or placement of an Ommaya reservoir. For DLBCL patients who present with active CSF involvement (known as lymphomatous meningitis), intrathecal chemotherapy treatments are typically given 2 or 3 times weekly until the CSF clears, followed by weekly intrathecal treatment for 4 weeks, and then monthly intrathecal treatment for 4 months [56]. For those with concurrent systemic and brain parenchymal DLBCL, a strategy of alternating R-CHOP with mid-cycle high-dose methotrexate can be successful. In addition, consolidation with high-dose therapy and auto-HCT improved survival in such patients in 1 retrospective series [57].
Relapsed/Refractory Disease. Between 30% and 40% of patients with advanced stage DLBCL will either fail to attain a remission with primary therapy (referred to as primary induction failure) or will relapse. In general, for those with progressive or relapsed disease, an updated tissue biopsy is recommended. This is especially true for patients who have had prior complete remission and have new lymph node enlargement, or those who have emergence of new sites of disease at the completion of first-line therapy.
Patients with relapsed disease are treated with systemic second-line platinum-based chemoimmunotherapy, with the usual goal of ultimately proceeding to auto-HCT. A number of platinum-based regimens have been used in this setting such as R-ICE, R-DHAP, R-GDP, R-Gem-Ox, and R-ESHAP. None of these regimens has been shown to be superior in terms of efficacy, and the choice of regimen is typically made based on the anticipated tolerance of the patient in light of comorbidities, laboratory studies, and physician preference. In the CORAL study, R-DHAP (rituximab, dexamethasone, high-dose cytarabine, cisplatin) seemed to show superior PFS in patients with the GCB subtype [58]. However, this was an unplanned subgroup analysis and R-DHAP was associated with higher renal toxicity.
Several studies have demonstrated that long-term PFS can be observed for relapsed/refractory DLBCL patients who respond to second-line therapy and then undergo high-dose therapy with auto-HCT. The Parma trial remains the only published prospective randomized trial performed in relapsed DLBCL comparing a transplant strategy to a non-transplant strategy. This study, performed in the pre-rituximab era, clearly showed a benefit in terms of DFS and OS in favor of auto-HCT versus salvage therapy alone [59]. The benefit of auto-HCT in patients treated in the rituximab era, even in patients who experience early failure (within 1 year of diagnosis), was confirmed in a retrospective analysis by the Center for International Blood and Marrow Transplant Research. In this study, a 44% 3-year PFS was seen in the early failure cohort versus 52% in the late failure cohort [60].
Some DLBCL patients are very unlikely to benefit from auto-HCT. The REFINE study focused on patients with primary induction failure or early relapse within 6 months of completing first-line therapy. Among such patients, primary progressive disease (defined as progression while still receiving first-line therapy), a high NCCN-IPI score at relapse, and MYC rearrangement were risk factors for poor PFS following auto-HCT [61]. Patients with 2 or 3 high-risk features had a 2-year OS of 10.7% compared to 74.3% for those without any high-risk features.
Allogeneic HCT (allo-HCT) is a treatment option for relapsed/refractory DLBCL. This option is more commonly considered for patients in whom an autotransplant has failed to achieve durable remission. For properly selected patients in this setting, a long-term PFS in the 30% to 40% range can be attained [62]. However, in practice, only about 20% of patients who fail auto-HCT end up undergoing allo-HCT due to rapid progression of disease, age, poor performance status, or lack of suitable donor. It has been proposed that in the coming years, allo-HCT will be utilized less commonly in this setting due to the advent of chimeric antigen receptor T-cell (CAR T) therapy.
CAR T-cell therapy genetically modifies the patient’s own T lymphocytes with a gene that encodes an antigen receptor to direct the T cells against lymphoma cells. Typically, the T cells are genetically modified and expanded in a production facility and then infused back into the patient. Axicabtagene ciloleucel is directed against the CD-19 receptor and has been approved by the US Food and Drug Administration (FDA) for treatment of patients with DLBCL who have failed 2 or more lines of systemic therapy. Use of CAR-T therapy in such patients was examined in a multicenter trial (ZUMA-1), which reported a 54% complete response rate and 52% OS rate at 18 months.63 CAR-T therapy is associated with serious side effects such as cytokine release syndrome, neurological toxicities, and prolonged cytopenias. While there are now some patients with ongoing remission 2 or more years after undergoing CAR-T therapy, it remains uncertain what proportion of patients have been truly cured with this modality. Nevertheless, this new treatment option remains a source of optimism for relapsed and refractory DLBCL patients.