Bridging Radiation Rapidly and Effectively Cytoreduces High-Risk Relapsed/Refractory Aggressive B Cell Lymphomas Prior to Chimeric Antigen Receptor T Cell Therapy

Efficient combination of radiotherapy and CAR-T - A systematic review

Chimeric antigen receptor T (CAR-T) cell therapy, a groundbreaking immunotherapy. However, it faces formidable challenges in treating solid tumors, grappling with issues like poor trafficking, limited penetration, and insufficient persistence within the tumor microenvironment (TME). CAR-T cells are engineered to express receptors that target specific cancer antigens, enhancing their ability to recognize and eliminate cancer cells. This review paper explores the intricate interplay between CAR-T therapy and radiotherapy (RT), investigating their synergistic potential. Radiotherapy, a standard cancer treatment, involves using high doses of radiation to target and damage cancer cells, disrupting their ability to grow and divide. We highlight that RT modulates the TME, augments antigen presentation, and promotes immune cell infiltration, bolstering CAR-T cell-mediated tumor eradication. Molecular insights shed light on RT-induced alterations in tumor stroma, T cell recruitment promotion, and induction of immunogenic cell death. Noteworthy, strategies, such as combining hypofractionated radiotherapy with myeloid-derived suppressor cell blockade, underscore innovative approaches to enhance CAR-T cell therapy in solid tumors. Bridging indications for RT and CAR-T cells in hematological malignancies are discussed, emphasizing scenarios where RT strategically enhances CAR-T cell efficacy. The paper critically evaluates the RT as a bridge compared to traditional chemotherapy, highlighting timing and dosage considerations crucial for optimizing CAR-T therapy outcomes. In summary, the paper provides valuable insights into the intricate molecular mechanisms activated by RT and innovative strategies to improve CAR-T cell therapy, fostering a deeper understanding of their combined potential in cancer treatment.

Outcome and feasibility of radiotherapy bridging in large B-cell lymphoma patients receiving CD19 CAR T in the UK

Radiotherapy (RT) has potential synergistic effects with chimeric antigen receptor (CAR) T but is not widely used as bridging therapy due to logistical challenges and lack of standardised protocols. We analysed RT bridging in a multicentre national cohort of large B-cell lymphoma patients approved for 3L axicabtagene ciloleucel or tisagenlecleucel across 12 UK centres. Of 763 approved patients, 722 were leukapheresed, 717 had data available on bridging therapy. 169/717 (24%) received RT bridging, 129 as single modality and 40 as combined modality treatment (CMT). Of 169 patients, 65.7% had advanced stage, 36.9% bulky disease, 86.5% elevated LDH, 41.7% international prognostic index (IPI) ≥3 and 15.2% double/triple hit at the time of approval. Use of RT bridging varied from 11% to 32% between centres and increased over time. Vein-to-vein time and infusion rate did not differ between bridging modalities. RT-bridged patients had favourable outcomes with 1-year progression-free survival (PFS) of 56% for single modality and 47% for CMT (1-year PFS 43% for systemic bridging). This is the largest cohort of LBCL patients receiving RT bridging prior to CAR T reported to date. Our results show that RT bridging can be safely and effectively used even in advanced stage and high-risk disease, with low dropout rates and excellent outcomes.

Reducing and controlling metabolic active tumor volume prior to CAR T-cell infusion can improve survival outcomes in patients with large B-cell lymphoma

Bridging therapy before CD19-directed chimeric antigen receptor (CAR) T-cell infusion is frequently applied in patients with relapsed or refractory Large B-cell lymphoma (r/r LBCL). This study aimed to assess the influence of quantified MATV and MATV-dynamics, between pre-apheresis (baseline) and pre-lymphodepleting chemotherapy (pre-LD) MATV, on CAR T-cell outcomes and toxicities in patients with r/r LBCL. MATVs were calculated semi-automatically at baseline (n = 74) and pre-LD (n = 68) in patients with r/r LBCL who received axicabtagene ciloleucel. At baseline, patients with a low MATV (< 190 cc) had a better time to progression (TTP) and overall survival (OS) compared to high MATV patients (p < 0.001). High MATV patients who remained stable or reduced upon bridging therapy showed a significant improvement in TTP (p = 0.041) and OS (p = 0.015), compared to patients with a high pre-LD MATV (> 480 cc). Furthermore, high MATV baseline was associated with severe cytokine release syndrome (CRS, p = 0.001). In conclusion, patients with low baseline MATV had the best TTP/OS and effective reduction or controlling MATV during bridging improved survival outcomes in patients with a high baseline MATV, providing rationale for the use of more aggressive bridging regimens.

Incorporating radiation with anti-CD19 chimeric antigen receptor T-cell therapy for relapsed/refractory non-Hodgkin lymphoma: A multicenter consensus approach

Anti-CD19 chimeric antigen receptor T-cell therapy (CART) has revolutionized the outcomes of relapsed and/or refractory B-cell non-Hodgkin lymphoma. However, CART is still limited by its availability, toxicity, and response durability. Not all patients make it to the CART infusion phase due to disease progression. Among those who receive CART, a significant number of patients experience life-threatening cytokine release syndrome toxicity, and less than half maintain a durable response with the majority relapsing in pre-existing sites of disease present pre-CART. Radiation therapy stands as a promising peri-CART and salvage treatment that can improve the outcomes of these patients. Evidence suggests that bridging radiotherapy prior to CART controls the disease during the manufacturing period, augments response rates and local control, cytoreduces/debulks the disease and decreases the severity of cytokine release syndrome, and may prolong disease-free intervals and survival especially in patients with bulky disease. Consolidative radiotherapy for residual post-CART disease alters the pattern of relapse and improves local recurrence-free and progression-free survivals. Salvage radiotherapy for relapsed post-CART disease has favorable survival outcomes when delivered comprehensively for patients with limited relapsed disease and palliates symptoms for patients with diffuse relapsed disease. The biology of the disease during the peri-CART period is poorly understood, and further studies investigating the optimal timing and dosing of radiation therapy (RT) are needed. In this review, we tackle the most significant challenges of CART, review and propose how RT can help mitigate these challenges, and provide The Mayo Clinic experts' approach on incorporating RT with CART.

CD19-directed CAR T cells as first salvage therapy for large B-cell lymphoma: towards a rational approach

The approval of CD19-directed chimeric antigen receptor (CAR) T-cell therapies for the second-line treatment of high-risk large B-cell lymphoma (LBCL) has greatly affected salvage algorithms for this condition, and such therapies could have the potential to improve the course of relapsed or refractory LBCL. In this Review, we provide guidance for a rational management approach to the use of commercial CD19-directed CAR T cells in the second-line treatment of LBCL, addressing crucial questions regarding eligible histologies; age, comorbidity, and tumour biology restrictions; the handling of very aggressive tumour behaviour; and holding and bridging therapies. The guidance was developed in a structured manner and, for each question, consists of a description of the clinical issue, a summary of the evidence, the rationale for a practical management approach, and recommendations. These recommendations could help to decide on the optimal management of patients with relapsed or refractory LBCL who are considered for second-line CAR T-cell treatment.

Very low-dose radiotherapy for extranodal marginal zone lymphoma of bronchus-associated lymphoid tissue

Extranodal marginal zone lymphoma of bronchus-associated lymphoid tissue (BALT) is a rare cancer for which optimal treatment strategies are undefined. Retrospective analyses suggest excellent outcomes with surgical resection for localized BALT lymphoma; however, the role of radiotherapy remains underexplored. We report the largest-to-date single-center analysis of 13 primary BALT lymphoma patients treated with radiotherapy. Of 15 treated lesions, we report a 100% response rate with complete response (CR) achieved in 67% of lesions. Among 10 lesions treated with very low-dose radiotherapy (VLDRT; 4 Gray [Gy]), 6 (60%) achieved a CR; among 5 lesions treated with full-dose radiotherapy (24-36 Gy), 4 (80%) achieved a CR. There were no local recurrences. Only one patient, treated with 30 Gy, developed an acute grade 3/4 toxic effect. There were no events of radiation-induced secondary malignancies. Our institutional experience indicates that radiotherapy, including VLDRT, is a safe and effective treatment for primary BALT lymphoma.

Broadening the horizon: potential applications of CAR-T cells beyond current indications

Engineering immune cells to treat hematological malignancies has been a major focus of research since the first resounding successes of CAR-T-cell therapies in B-ALL. Several diseases can now be treated in highly therapy-refractory or relapsed conditions. Currently, a number of CD19- or BCMA-specific CAR-T-cell therapies are approved for acute lymphoblastic leukemia (ALL), diffuse large B-cell lymphoma (DLBCL), mantle cell lymphoma (MCL), multiple myeloma (MM), and follicular lymphoma (FL). The implementation of these therapies has significantly improved patient outcome and survival even in cases with previously very poor prognosis. In this comprehensive review, we present the current state of research, recent innovations, and the applications of CAR-T-cell therapy in a selected group of hematologic malignancies. We focus on B- and T-cell malignancies, including the entities of cutaneous and peripheral T-cell lymphoma (T-ALL, PTCL, CTCL), acute myeloid leukemia (AML), chronic myeloid leukemia (CML), chronic lymphocytic leukemia (CLL), classical Hodgkin-Lymphoma (HL), Burkitt-Lymphoma (BL), hairy cell leukemia (HCL), and Waldenström's macroglobulinemia (WM). While these diseases are highly heterogenous, we highlight several similarly used approaches (combination with established therapeutics, target depletion on healthy cells), targets used in multiple diseases (CD30, CD38, TRBC1/2), and unique features that require individualized approaches. Furthermore, we focus on current limitations of CAR-T-cell therapy in individual diseases and entities such as immunocompromising tumor microenvironment (TME), risk of on-target-off-tumor effects, and differences in the occurrence of adverse events. Finally, we present an outlook into novel innovations in CAR-T-cell engineering like the use of artificial intelligence and the future role of CAR-T cells in therapy regimens in everyday clinical practice.

CAR-T Cell Therapy in Large B Cell Lymphoma

Large B-cell lymphomas (LBCLs) are among the most frequent (about 30%) non-Hodgkin's lymphoma. Despite the aggressive behavior of these lymphomas, more than 60% of patients can be cured with first-line chemoimmunotherapy using the R-CHOP regimen. Patients with refractory or relapsing disease show a poor outcome even when treated with second-line therapies. CD19-targeted chimeric antigen receptor (CAR) T-cells are emerging as an efficacious second-line treatment strategy for patients with LBCL. Three CD19-CAR-T-cell products received FDA and EMA approval. CAR-T cell therapy has also been explored for treating high-risk LBCL patients in the first-line setting and for patients with central nervous system involvement. Although CD19-CAR-T therapy has transformed the care of refractory/relapsed LBCL, about 60% of these patients will ultimately progress or relapse following CD19-CAR-T; therefore, it is fundamental to identify predictive criteria of response to CAR-T therapy and to develop salvage therapies for patients relapsing after CD19-CAR-T therapies. Moreover, ongoing clinical trials evaluate bispecific CAR-T cells targeting both CD19 and CD20 or CD19 and CD22 as a tool to improve the therapeutic efficacy and reduce the number of refractory/relapsing patients.

Intrinsic tumor resistance to CAR T cells is a dynamic transcriptional state that is exploitable with low-dose radiation

Chimeric antigen receptor (CAR) T-cell therapy represents a major advancement for hematologic malignancies, with some patients achieving long-term remission. However, the majority of treated patients still die of their disease. A consistent predictor of response is tumor quantity, wherein a higher disease burden before CAR T-cell therapy portends a worse prognosis. Focal radiation to bulky sites of the disease can decrease tumor quantity before CAR T-cell therapy, but whether this strategy improves survival is unknown. We find that substantially reducing systemic tumor quantity using high-dose radiation to areas of bulky disease, which is commonly done clinically, is less impactful on overall survival in mice achieved by CAR T cells than targeting all sites of disease with low-dose total tumor irradiation (TTI) before CAR T-cell therapy. This finding highlights another predictor of response, tumor quality, the intrinsic resistance of an individual patient's tumor cells to CAR T-cell killing. Little is known about whether or how an individual tumor's intrinsic resistance may change under different circumstances. We find a transcriptional "death receptor score" that reflects a tumor's intrinsic sensitivity to CAR T cells can be temporarily increased by low-dose TTI, and the timing of this transcriptional change correlates with improved in vivo leukemia control by an otherwise limited number of CAR T cells. This suggests an actionable method for potentially improving outcomes in patients predicted to respond poorly to this promising therapy and highlights that intrinsic tumor attributes may be equally or more important predictors of CAR T-cell response as tumor burden.

Integrating CAR-T cell therapy into the management of DLBCL: what we are learning

INTRODUCTION

Chimeric Antigen Receptor ;(CAR) T cells therapies have become part of the standard of care for patients with relapsed/refractory (R/R) diffuse large B-cell lymphoma (DLBCL). The weakness of CAR-T therapies is that there are no comparative clinical trials, although many publications based on real-life data have confirmed the results obtained in pivotal studies. After several years of the commercialization of CAR-T, some points still need to be fully clarified. Healthcare professionals have questions about identifying patients who may benefit from therapy. There are aspects inherent in the accessibility of care related to improved relationships between CAR-T-delivering and referral centers.

AREAS COVERED

Open questions are inherent in the salvage and bridge therapy, predictive criteria for response and persistence of CAR-T after infusion. Managing toxicities remain a top priority and one of the points on which further knowledge is needed.

EXPERT OPINION

This review aims to describe the current landscape of CAR-T cells in DLBCL, outline their outcomes and toxicities, and explain the outstanding questions that remain to be addressed.

Reappraisal of the role of radiation therapy in lymphoma treatment

Radiation therapy (RT) for lymphomas has improved dramatically with modern imaging and treatment techniques, encompassing only the necessary volume with minimal doses to normal structures. Prescribed radiation doses are reduced, and fractionation schedules are under revision. With effective systemic treatment only initial macroscopic disease is irradiated. With no or less effective systemic treatment, possible microscopic disease is also included. Risks of long-term side effects of RT have diminished dramatically and should be weighed against risks from more systemic treatment or increased risk of relapse. Lymphoma patients are often elderly, they tolerate modern limited RT very well. Lymphomas refractory to systemic treatments often remain radioresponsive, and brief, mild RT may offer effective palliation. New roles for RT are emerging with immune therapies. RT for "bridging," keeping the lymphoma under control while waiting for immune therapy, is well established. Enhancement of the immune response to lymphomas, so-called "priming," is being intensively researched.