Autologous stem cell transplantation for primary mediastinal B-cell lymphoma: long-term outcome and role of post-transplant radiotherapy. A report of the European Society for Blood and Marrow Transplantation

Axicabtagene ciloleucel treatment is more effective in primary mediastinal large B-cell lymphomas than in diffuse large B-cell lymphomas: the Italian CART-SIE study

Axicabtagene ciloleucel showed efficacy for relapsed/refractory large B-cell lymphomas (LBCL), including primary mediastinal B-cell lymphomas (PMBCL); however, only few PMBCLs were reported. Aim was to evaluate efficacy and safety of axicabtagene ciloleucel in patients with PMBCL compared to those with other LBCL, enrolled in the Italian prospective observational CART-SIE study. PMBCLs (n = 70) were younger, with higher percentage of bulky and refractory disease, compared to other LBCLs (n = 190). Median follow-up time for infused patients was 12.17 months (IQR 5.53,22.73). The overall (complete + partial) response rate (ORR,CR + PR) after bridging was 41% for PMBCL and 28% for other LBCL, p = 0.0102. Thirty days ORR was 78% (53/68) with 50% (34) CR in PMBCL, and 75% (141/187) with 53% (100) CR in other LBCL, p = 0.5457. Ninety days ORR was 69% (45/65) with 65% (42) CR in PMBCL, and 54% (87/162) with 47% (76) CR in other LBCL; progressive disease was 21% in PMBCL and 45% in other LBCL, p = 0.0336. Twelve months progression-free survival was 62% (95% CI: 51-75) in PMBCL versus 48% (95% CI: 41-57) in other LBCL, p = 0.0386. Twelve months overall survival was 86% (95% CI: 78-95) in PMBCL versus 71% (95% CI: 64-79) in other LBCL, p = 0.0034. All grade cytokine release syndrome was 88% (228/260); all grade neurotoxicity was 34% (88/260), with 6% of fatal events in PMBCL. Non-relapse mortality was 3%. In conclusion, PMBCLs achieved significantly better response and survival rates than other LBCLs.

[Progress in treatment of primary mediastinal large B-cell lymphoma]

Primary mediastinal large B-cell lymphoma (PMBCL) is an aggressive B-cell lymphoma originating from the thymus, which has different clinical and biological characteristics from diffuse large B-cell lymphoma, NOS. PMBCL tends to occur in young women, usually presenting as a large anterior mediastinal mass. Most patients are in stage Ⅰ-Ⅱ at the time of presentation. There is no standard prognostic scoring system for PMBCL. Immunochemotherapy is commonly used in the treatment of PMBCL, but the optimal first-line treatment has not been determined, and the status of radiotherapy is controversial. The value of PET-CT guided therapy needs to be further verified. Relapsed/refractory PMBCL has a poor prognosis, while novel therapies such as PD-1 inhibitors, brentuximab vedotin, and CAR-T can help improve survival in these patients.

Updates in the Management of Primary Mediastinal B Cell Lymphoma

Primary mediastinal B cell lymphoma (PMBCL) is considered a distinct pathology according to the WHO classification of lymphoid malignancies. Patients have a better prognosis after the addition of Rituximab to anthracycline-based chemotherapy. The role of consolidative radiotherapy is controversial after the approval of dose-adjusted R-EPOCH and the selection of patients to undergo radiotherapy is based on end-of-therapy PET CT. In the relapsed/refractory setting, new approved drugs and other under investigation have improved patient outcomes. This review summarizes the different treatment modalities in (PMBCL) in the frontline and the relapsed/refractory settings.

High-Dose Chemotherapy and Autologous Stem Cell Transplantation for Relapsed or Refractory Primary Mediastinal Large B-Cell Lymphoma

Primary mediastinal large B-cell lymphoma (PMBCL) is an uncommon, aggressive type of non-Hodgkin lymphoma. Rituximab-containing chemoimmunotherapy with or without radiation therapy (RT) is standard first-line treatment. Relapsed or refractory (R/R) disease has long been treated with salvage chemotherapy followed by high-dose chemotherapy (HDC), with autologous stem cell transplantation (ASCT) in appropriate patients. We retrospectively analyzed all patients with R/R PMBCL treated with HDC/ASCT at our center between January 2000 and August 2022. The 60 study patients received either rituximab-BEAM (n = 37) or rituximab-gemcitabine/busulfan/melphalan (R-GemBuMel) with or without vorinostat (n = 23), followed by ASCT. Forty-six patients received mediastinal RT, either as prior consolidation of frontline therapy or following ASCT. At median follow-up of 6 years (range, .3 to 21 years), the 5-year progression-free survival (PFS) and overall survival (OS) rates of the whole group were 58% and 77%, respectively, for the entire cohort, 51% and 65% for the R-BEAM recipients, and 69% and 82% for R-vorinostat/GemBuMel recipients. Multivariable analyses showed that a negative positron emission tomography scan at ASCT (hazard ratio [HR], .28) and involvement of only 1 organ (HR, .33) were independently associated with improved PFS. In addition, receipt of R-vorinostat/GemBuMel (HR, .23) was an independent favorable predictor of OS. Our data indicate that HDC/ASCT is effective in R/R PMBCL, with improved outcomes in patients receiving R-vorinostat/GemBuMel.

Pediatric Aggressive Mature B-Cell Lymphomas, Version 3.2022, NCCN Clinical Practice Guidelines in Oncology

NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines) for Pediatric Aggressive Mature B-Cell Lymphomas include recommendations for the diagnosis and management of pediatric patients with primary mediastinal large B-cell lymphoma (PMBL) and sporadic variants of Burkitt lymphoma and diffuse large B-cell lymphoma. PMBL is now considered as a distinct entity arising from mature thymic B-cells accounting for 2% of mature B-cell lymphomas in children and adolescents. This discussion section includes the recommendations outlined in the NCCN Guidelines for the diagnosis and management of pediatric patients with PMBL.

Outcomes after first-line immunochemotherapy for primary mediastinal B-cell lymphoma: a LYSA study

Primary mediastinal B-cell lymphoma (PMBL) is a rare type of aggressive lymphoma typically affecting young female patients. The first-line standard of care remains debated. We performed a large multicenter retrospective study in 25 centers in France and Belgium to describe PMBL patient outcomes after first-line treatment in real-life settings. A total of 313 patients were enrolled and received rituximab (R) plus ACVBP (doxorubicin, cyclophosphamide, vindesine, bleomycin, and prednisone) (n = 180) or CHOP (cyclophosphamide, doxorubicin, vincristine, and prednisone) delivered every 14 days (R-CHOP14, n = 76) or 21 days (R-CHOP21, n = 57) and consolidation strategies in modalities that varied according to time and institution, mainly guided by positron emission tomography. Consolidation autologous stem cell transplantation was performed for 46 (25.6%), 24 (31.6%), and 1 (1.8%) patient in the R-ACVBP, R-CHOP14, and R-CHOP21 groups, respectively (P < .001); only 17 (5.4%) patients received mediastinal radiotherapy. The end-of-treatment complete metabolic response rates were 86.3%, 86.8%, and 76.6% (P = .23) in the R-ACVBP, R-CHOP14, and R-CHOP21 groups. The median follow-up was 44 months, and the R-ACVBP, R-CHOP14, and R-CHOP21 three-year progression-free survival probabilities were 89.4% (95% confidence interval [CI], 84.8-94.2), 89.4% (95% CI, 82.7-96.6), and 74.7% (95% CI, 64-87.1) (P = .018). A baseline total metabolic tumor volume (TMTV) ≥360 cm3 was associated with a lower progression-free survival (hazard ratio, 2.18; 95% CI, 1.05-4.53). Excess febrile neutropenia (24.4% vs 5.3% vs 5.3%; P < .001) and mucositis (22.8% vs 3.9% vs 1.8%; P < .001) were observed with R-ACVBP compared with the R-CHOP regimens. Patients with PMBL treated with dose-dense immunochemotherapy without radiotherapy have excellent outcomes. R-ACVBP acute toxicity was higher than that of R-CHOP14. Our data confirmed the prognostic importance of baseline TMTV.

Primary mediastinal Large B-cell Lymphoma

Primary mediastinal large B-cell lymphoma (PMBCL) is a separate entity in the WHO classification based on clinico-pathologic features and a distinct molecular signature which overlaps with nodular sclerosis classical Hodgkin lymphoma (NScHL). Molecular classifiers can distinguish PMBCL from diffuse large B-cell lymphoma (DLBCL) using RNA derived from paraffin-embedded tissue and are integral to future studies. However, given that ~5% of DLBCL can have a 'molecular' PMBCL phenotype in the absence of mediastinal involvement, clinical information will remain critical for diagnosis. Studies over the last 10-20 years have elucidated the biologic hallmarks of PMBCL which are reminiscent of cHL, including the importance of JAK-STAT and NFKB signaling pathways as well as an immune evasion phenotype through multiple converging genetic aberrations. The outcome of PMBCL has improved in the modern rituximab era, however controversies remain whether there is a single standard treatment for all patients and when to integrate radiotherapy. Regardless of the frontline therapy, refractory disease can occur in up to 10% of patients and correlates with poor outcome. With emerging data supporting high efficacy of PD1 inhibitors in PMBCL, studies are underway integrating them into the up-front setting.

Pembrolizumab in the treatment of refractory primary mediastinal large B-cell lymphoma: safety and efficacy

Introduction: Primary mediastinal large B-cell lymphoma (PMBL) is a rare subtype of lymphoma, clinically and biologically distinct from diffuse large B-cell lymphoma (DLBCL) that shows overlapping features with classical Hodgkin lymphoma (cHL). If first-line strategies lead to 80-85% of curability, relapse occurs early with a chemo-refractory disease and a poor outcome. The presence of 9p24.1 rearrangement, conducting to the overexpression of the immune checkpoint molecules PDL1 and 2, has paved the way for immune checkpoint blockers development in these entities. Pembrolizumab, an anti PD-1 checkpoint antibody, was initially approved in solid cancer and later on in the lymphoma field in cHL.Areas covered: We summarize the biology and clinical need in PMBL, leading to the rationale for checkpoint inhibitors development, as well as pembrolizumab clinical studies in this entity. To do so, we performed a PubMed search using the terms: 'PMBCL,' 'lymphoma,' 'Immune checkpoint,' and 'Pembrolizumab.'Expert opinion: Pembrolizumab showed tolerable safety profile and efficacy data in patients with PMBL who have relapsed after, or are ineligible for autologous stem cell transplant (ASCT). Some combination strategies have shown promising preliminary results, while others are currently being conducted.

Primary Mediastinal B Cell Lymphoma in the Positron-Emission Tomography Era Executive Summary of the American Radium Society Appropriate Use Criteria

PURPOSE

Primary mediastinal B cell lymphoma (PMBCL) is a highly curable subtype of non-Hodgkin lymphoma that is diagnosed predominantly in adolescents and young adults. Consequently, long-term treatment-related morbidity is critical to consider when devising treatment strategies that include different chemoimmunotherapy strategies with or without radiation therapy. Furthermore, adaptive approaches using the end-of-chemotherapy (EOC) positron emission tomography (PET)/computed tomography (CT) scanning may help to determine which patients may benefit from additional therapies. We aimed to develop evidence-based guidelines for treating these patients.

METHODS AND MATERIALS

We conducted a systematic review in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guideline using the PubMed database. The ARS expert committee, composed of radiation oncologists, hematologists, and pediatric oncologists, developed consensus guidelines using the modified Delphi framework.

RESULTS

Nine studies met the full criteria for inclusion based on reporting outcomes on patients with primary mediastinal B cell lymphoma with EOC PET/CT response scored with the 5-point Deauville scale. These studies formed the evidence for these guidelines in managing patients with PMBCL according to the EOC PET response, including after a 5-point Deauville scale of 1 to 3, 4, or 5, and for patients with relapsed and refractory disease. The expert group also developed guidance on radiation simulation, treatment planning, and plan evaluation based on expert opinion.

CONCLUSIONS

Various treatment approaches exist in the management of PMBCL, including different chemoimmunotherapy regimens, the use of consolidative radiation therapy, and adaptive approaches based on EOC PET/CT response. These guidelines can be used by practitioners to provide appropriate treatment according to different disease scenarios.

Primary Mediastinal B-Cell Lymphoma: Novel Precision Therapies and Future Directions

Primary mediastinal large B-cell lymphoma (PMBCL) is a distinct clinicopathologic disease from other types of diffuse large B-cell lymphoma (DLBCL) with unique prognostic features and limited availability of clinical data. The current standard treatment for newly diagnosed PMBCL has long been dependent on a dose-intensive, dose-adjusted multi-agent chemotherapy regimen of rituximab plus etoposide, prednisone, vincristine, cyclophosphamide, and doxorubicin (DA-R-EPOCH). Recent randomized trials have provided evidence that R-CHOP followed by consolidation radiotherapy (RT) is a valuable alternative option to first-line treatment. For recurrent/refractory PMBCL (rrPMBCL), new drugs such as pembrolizumab and CAR-T cell therapy have proven to be effective in a few studies. Positron emission tomography-computed tomography (PET-CT) is the preferred imaging modality of choice for the initial phase of lymphoma treatment and to assess response to treatment. In the future, baseline quantitative PET-CT can be used to predict prognosis in PMBCL. This review focuses on the pathology of PMBCL, underlying molecular basis, treatment options, radiotherapy, targeted therapies, and the potential role of PET-CT to guide treatment choices in this disease.

Allogeneic Stem Cell Transplantation Provides Durable Remission in Patients with Primary Mediastinal Large B Cell Lymphoma

Standard therapy for relapsed or refractory (rel/ref) primary mediastinal large B cell lymphoma (PMBCL) is salvage therapy followed by autologous (auto) hematopoietic stem cell transplantation (HSCT). However, many patients have refractory disease and are unable to undergo autoHSCT, and a sizeable proportion of patients will relapse after autoHSCT. By analogy to diffuse large B cell lymphoma, these patients may be treated with allogeneic (allo) HSCT with curative intent, but at the risk of significant morbidity and mortality. Given the advent of effective immunotherapy approaches for rel/ref PMBCL, it is important to better understand the toxicity and efficacy of alloHSCT in these patients, to which these new approaches could be an alternative. Therefore, we retrospectively studied the outcomes of alloHSCT in a multicenter cohort of 28 patients with rel/ref PMBCL who underwent transplantation at 4 centers. Most patients (79%) were sensitive to pretransplantation therapy and 86% received reduced-intensity conditioning. The overall progression-free survival (PFS), overall survival (OS), and cumulative incidences of nonrelapse mortality and relapse in the cohort at 5 years were 34%, 45%, 32%, and 33%, respectively. Outcomes were significantly better in patients with pretransplantation responsive disease (2-year PFS and OS of 50% and 58%, respectively) compared with refractory patients (2-year PFS and OS of 0%). In our multicenter retrospective study, alloHSCT produced durable remissions in a proportion of patients with treatment-sensitive disease before transplantation (5-year PFS of 44%) and should be considered in the treatment of patients with rel/ref PMBCL.

Outcomes of Relapsed and Refractory Primary Mediastinal (Thymic) Large B Cell Lymphoma Treated with Second-Line Therapy and Intent to Transplant

Primary mediastinal (thymic) large B cell lymphoma is a subtype of diffuse large B cell lymphoma with distinct clinical, molecular, and genetic features, many of which overlap with Hodgkin lymphoma. Increasingly, initial therapy for these patients has used dose-dense chemotherapy with or without radiation with excellent results. In patients with relapsed and primary refractory disease, outcomes of second-line therapy followed by consolidation with high-dose therapy and autologous stem cell transplantation remains largely undefined. We reviewed the outcomes of 60 transplant-eligible patients with relapsed or refractory primary mediastinal (thymic) large B cell lymphoma enrolled on sequential protocols with uniform second-line therapy with intent to consolidate with autologous stem cell transplant. The estimated 3-year overall and event-free survivals for all patients were 61% and 57%, respectively, and 68% and 65%, respectively, for patients proceeding to stem cell transplant. Multivariable analysis of risk factors before transplant revealed that an incomplete response to initial therapy, advanced Ann Arbor stage at disease progression, and failure to achieve a partial remission or better to second-line therapy to be independently associated with inferior event-free and overall survival. A risk score based on these variables was able to identify patients who are unlikely to respond to conventional second-line strategies. These results suggest that salvage chemoradiotherapy with intent of subsequent high-dose therapy and autologous stem cell transplant is successful in most patients with relapsed and refractory primary mediastinal (thymic) large B cell lymphoma. Alternative strategies are warranted for a significant subset of patients with high-risk disease who are unlikely to be cured with this strategy.