Positron emission tomography after response to rituximab-CHOP in primary mediastinal large B-cell lymphoma: impact on outcomes and radiotherapy strategies

PET/CT in Non-Hodgkin Lymphoma: An Update

Non-Hodgkin lymphomas represents a heterogeneous group of lymphoproliferative disorders characterized by different clinical courses, varying from indolent to highly aggressive. ¹⁸F-FDG-PET/CT is the current state-of-the-art diagnostic imaging, for the staging, restaging and evaluation of response to treatment in lymphomas with avidity for ¹⁸F-FDG, despite it is not routinely recommended for surveillance. PET-based response criteria (using five-point Deauville Score) are nowadays uniformly applied in FDG-avid lymphomas. In this review, a comprehensive overview of the role of ¹⁸F-FDG-PET in Non-Hodgkin lymphomas is provided, at each relevant point of patient management, particularly focusing on recent advances on diffuse large B-cell lymphoma and follicular lymphoma, with brief updates also on other histotypes (such as marginal zone, mantle cell, primary mediastinal- B cell lymphoma and T cell lymphoma). PET-derived semiquantitative factors useful for patient stratification and prognostication and emerging radiomics research are also presented.

Treatment options in primary mediastinal B cell lymphoma patients, retrospective multicentric analysis; a Turkısh oncology group study

Introduction and Aim

Primary mediastinal B-cell lymphomas (PMBL) are aggressive B- cell lymphomas. Although the initial treatment models vary in PMBL, appropriate treatment methods are not known. We aim to show real-life data on health outcomes in adult patients with PMBL who received various type of chemoimmunotherapies in Turkey.

Method

We analyzed the data of 61 patients who received treatments for PMBL from 2010 to 2020. The overall response rate (ORR), overall survival (OS) and progression-free survival (PFS) of the patients were evaluated.

Results

61 patients were observed in this study. The mean age of the study group was 38.4 ± 13.5 years. From among them, 49.2% of the patients were female (n = 30). For first-line therapy, 33 of them had received rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP) regimen (54%). Twenty-five patients had received rituximab, etoposide, prednisone, vincristine, cyclophosphamide and doxorubicin (DA-EPOCH-R) regimen. The ORR was 77%. The median OS and PFS were as follows: 25 months (95% CI: 20.4-29.4) and 13 months (95% CI: 8.6-17.3), respectively. The OS and PFS at 12 months were 91.3% and 50%, respectively. The OS and PFS at five years were 64.9% and 36.7%, respectively. Median follow-up time period was 20 months (IQR 8.5-38.5).

Conclusion

R-CHOP and DA-EPOCH-R showed good results in PMBL. These remain one of the best determined systemic treatment options for first-line therapy. Also, the treatment was associated with good efficacy and tolerability.

Very Early Onset of Therapy-Related Acute Myeloid Leukemia with 11q23 Rearrangement Presenting with Unusual PET Findings after R-DA-EPOCH for Primary Mediastinal Large B-Cell Lymphoma

Background: R-DA-EPOCH is an effective regimen for PMLBCL, which permits the omission of consolidative radiotherapy in the majority of patients. Patient: We describe a 27-year-old female patient, who achieved a complete remission after treatment with six cycles of R-DA-EPOCH (up to the final level). At 6 months after the end of treatment, PET/CT revealed an unexpected, diffusely increased 18FDG uptake by the bone marrow. Simultaneously, pancytopenia with monocytosis was observed. Result: The patient was diagnosed with therapy-related myelodysplastic syndrome, which rapidly evolved into acute myeloid leukemia (t-MDS/AML) with MLL rearrangements. She achieved a complete remission after induction therapy, received an allogenic transplant and remains disease-free 2 years later. Conclusions: The extremely early onset of t-MDS/AML, together with the unexpected PET/CT findings make this case unique and highlights the need for the accurate estimation of the possible dose-dependent risk of t-MDS/AML after R-DA-EPOCH in the real-life setting in patients with PMLBCL.

Dose-adjusted EPOCH-R is not superior to sequential R-CHOP/R-ICE as a frontline treatment for newly diagnosed primary mediastinal B-cell lymphoma: Results of a bi-center retrospective study

Purpose

Primary mediastinal B‐cell lymphoma (PMBCL) is a rare subtype of diffuse large B‐cell lymphoma (DLBCL). Despite its aggressive course, PMBCL is considered curable. While in recent years dose‐adjusted (DA) EPOCH‐R (rituximab, etoposide, prednisone, vincristine, cyclophosphamide and doxorubicin) has become widely endorsed as first‐line therapy for newly‐diagnosed PMBCL, the optimal treatment for this disease and the role of radiotherapy (RT) remains unclear. DA‐EPOCH‐R provides good clinical outcomes, albeit is associated with short‐ and long‐term toxicity. To address this issue, the current retrospective bi‐icenter analysis compared efficacy and toxicity of DA‐EPOCH‐R and a less toxic R‐CHOP/R‐ICE regimen used for the treatment of newly‐diagnosed PMBCL.

Patients and Methods

The study included all patients with a histologically confirmed PMBCL diagnosis treated with DA‐EPOCH‐R or R‐CHOP/R‐ICE between 01/2013‐12/2020 at two tertiary medical centers. Patient demographic and clinical data were derived from institutional electronic medical records. The analysis included 56 patients: 31 received DA‐EPOCH‐R and 25 – R‐CHOP/R‐ICE.

Results

At a median follow‐up of 1.9 years (IQR 3.1 years), similar progression‐free survival (2.1 versus 2.4 years; p = 0.7667), overall survival (2.5 versus 2.7 years; p = 0.8047) and complete response (80%) were observed in both groups. However, DA‐EPOCH‐R was associated with significantly longer hospitalization required for its administration (p < 0.001) and a trend for higher frequency of infections, stomatitis, thrombotic complications and febrile neutropenia‐related hospitalizations.

Conclusion

DA‐EPOCH‐R and R‐CHOP/R‐ICE provide similarly encouraging outcomes in newly‐diagnosed PMBCL patients. R‐CHOP/R‐ICE is associated with lower toxicity and significantly reduced hospitalization. Our findings suggest that this regimen may be considered as an alternative to DA‐EPOCH‐R in this patient population.

Current and emerging treatment options in primary mediastinal B-cell lymphoma

Previously considered a subtype of diffuse large B-cell lymphoma (DLBCL), primary mediastinal B-cell lymphoma (PMBCL) is now recognized by the World Health Organization as an independent entity. PMBCL has clinicopathologic features that are separate from systemic DLBCL and harbors some biologic characteristics which overlap with nodular sclerosing classic Hodgkin’s lymphoma (cHL). Similar to cHL, copy number alterations of 9p24.1 are frequently seen in PMBCL, which leads to increased expression of key genes in the region, including programmed death-ligand 1( PD-L1), PD-L2, and JAK2. In addition, PMBCL cells express CD30 in a mostly patchy fashion. In the upfront setting, dose-adjusted etoposide, prednisone, vincristine, cyclophosphamide, doxorubicin, and rituximab (i.e., DA-EPOCH-R) is the only regimen that has been shown in a prospective setting to result in outstanding outcomes without consolidative radiation to the mediastinum, with a 5-year event-free survival rate of 93% and overall survival rate of 97%. Thus, in recent years, DA-EPOCH-R has been recognized as the preferred frontline regimen. Despite the encouraging results in the frontline setting, the outcomes in the relapsed/refractory setting remain poor. The current approach of salvage chemotherapy followed by autologous stem cell transplantation, as used in patients with DLBCL, does not result in high rates of cure in patients with rrPMBCL. In recent years, the characteristic molecular features identified in PMBCL have provided more treatment opportunities for this patient population. In the relapsed setting, single-agent PD-1 inhibitor pembrolizumab have demonstrated high and durable remission rates. Despite the expression of CD30, the CD30 antibody drug-conjugate brentuximab vedotin (BV) as a single agent has been deemed inactive in this disease. On the contrary, the combinations of BV and PD-1 inhibitor have shown higher response rates than PD-1 inhibitor alone. Moreover, anti-CD19 chimeric antigen receptor T-cell (CAR T-cell) therapy has been positioned as another successful strategy for patients with rrPMBCL. Axicabtagene ciloleucel and lisocabtagene maraleucel are two products used in rrPMBCL.

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.

Identification of Very Low-Risk Subgroups of Patients with Primary Mediastinal Large B-Cell Lymphoma Treated with R-CHOP

BACKGROUND

R-CHOP can cure approximately 75% of patients with primary mediastinal large B-cell lymphoma (PMLBCL), but prognostic factors have not been sufficiently evaluated yet. R-da- EPOCH is potentially more effective but also more toxic than R-CHOP. Reliable prognostic classification is needed to guide treatment decisions.

MATERIALS AND METHODS

We analyzed the impact of clinical prognostic factors on the outcome of 332 PMLBCL patients ≤65 years treated with R-CHOP ± radiotherapy in a multicenter setting in Greece and Cyprus.

RESULTS

With a median follow-up of 69 months, 5-year freedom from progression (FFP) was 78% and 5-year lymphoma specific survival (LSS) was 89%. On multivariate analysis, extranodal involvement (E/IV) and lactate dehydrogenase (LDH) ≥2 times upper limit of normal (model A) were significantly associated with FFP; E/IV and bulky disease (model B) were associated with LSS. Both models performed better than the International Prognostic Index (IPI) and the age-adjusted IPI by Harrel's C rank parameter and Akaike information criterion. Both models A and B defined high-risk subgroups (13%-27% of patients [pts]) with approximately 19%-23% lymphoma-related mortality. They also defined subgroups composing approximately one-fourth or one-half of the patients, with 11% risk of failure and only 1% or 4% 5-year lymphoma-related mortality.

CONCLUSION

The combination of E/IV with either bulky disease or LDH ≥2 times upper limit of normal defined high-risk but not very-high-risk subgroups. More importantly, their absence defined subgroups comprising approximately one-fourth or one-half of the pts, with 11% risk of failure and minimal lymphoma-related mortality, who may not need more intensive treatment such as R-da-EPOCH.

IMPLICATIONS FOR PRACTICE

By analyzing the impact of baseline clinical characteristics on outcomes of a large cohort of patients with primary mediastinal large B-cell lymphoma homogeneously treated with R-CHOP with or without radiotherapy, we developed novel prognostic indices which can aid in deciding which patients can be adequately treated with R-CHOP and do not need more intensive regimens such as R-da-EPOCH. The new indices consist of objectively determined characteristics (extranodal disease or stage IV, bulky disease, and markedly elevated serum lactate dehydrogenase), which are readily available from standard initial staging procedures and offer better discrimination compared with established risk scores (International Prognostic Index [IPI] and age-adjusted IPI).