Role of Consolidative Radiation Therapy Following Autologous Stem Cell Transplant for Relapsed or Refractory Diffuse Large B-Cell Lymphoma

'Le Roi est mort, vive le Roi': New Roles of Radiotherapy in the Treatment of Lymphomas in Combination With Immunotherapy

BACKGROUND

immunotherapy (IT), including checkpoint inhibitors (CIs) and Chimeric Antigen Receptor T cell therapy (CAR-T) revolutionized the treatment of relapsing or refractory (r/r) lymphoma. Several preliminary experiences evaluated concomitant administration of radiotherapy and IT.

METHODS

we performed a systematic review of current literature as of March 30, 2020. A total of 1090 records was retrieved, 42 articles were selected on the basis of title and abstract and, after the removal of analyses with no original data or insufficient clinical information, 28 papers were included in the review.

RESULTS

previous studies were mostly represented by case reports/series or small cohorts. Nonetheless, combination of radiotherapy and CIs or CAR-T led to promising outcomes, resulting in extremely high rates of complete response and improving progression free and overall survival compared with data from recent clinical trials. Combination of RT and CIs had a fair toxicity profile with no reports of severe side effects. Within the limits of the small cohorts retrieved, RT seems a superior option compared with systemic treatment as a 'bridge' to CAR-T and could as well reduce severe complications rates. Radiotherapy could elicit immune response against lymphoma, as demonstrated by multiple cases of abscopal effect and its inclusion in anti-neoplastic vaccines protocols.

CONCLUSION

The results of this review warrant the evaluation of combination of RT and immunotherapy in larger and preferably prospective and randomized cohorts to confirm these preliminary impressive outcomes. The optimal dose, fractionation and timing of RT still have to be clarified.

Palliative Radiotherapy for Diffuse Large B-cell Lymphoma

Recent improvements in chemoimmunotherapies, targeted agents, hematopoietic stem cell transplants, and cellular therapies have revolutionized treatment paradigms for patients with diffuse large B-cell lymphoma (DLBCL). Even in the relapsed or refractory setting, contemporary treatment options are delivered with curative intent and can lead to lasting remissions. Although such therapies have improved overall outcomes, they have increasingly led to a wide variety of presentations of recurrent tumors in need of palliation. Here, we review the use of radiotherapy (RT) in the palliation of DLBCL. We draw particular attention to the evolving role for hypofractionated RT and low-dose RT for DLBCL. We review the available literature on these topics and focus on commonly encountered clinical scenarios.

Radiotherapy for Non-Hodgkin Lymphomas

Radiotherapy (RT) plays a diverse and essential role in the contemporary management of non-Hodgkin lymphoma (NHL) and remains the single most powerful monotherapeutic intervention for both aggressive and indolent subtypes. Over the past decade, there have been significant advancements in radiation oncology practice, which have made modern treatments safer and more conformal. Despite this sophistication and evidence supporting a continued role for RT, numerous data suggest that utilization is on the decline. In this review, we discuss the rationale for RT in 4 commonly encountered scenarios: combined modality therapy for limited-stage aggressive NHL, consolidation therapy for advanced-stage aggressive NHL, and the changing roles of salvage RT for relapsed/refractory NHL in an era of new frontiers such as cellular therapies. We also evaluate current strategies to treat indolent histologies. We conclude with perspectives on how RT for the hematological malignancies may continue to evolve.

Early experience using salvage radiotherapy for relapsed/refractory non-Hodgkin lymphomas after CD19 chimeric antigen receptor (CAR) T cell therapy

Radiotherapy is potentially an important salvage strategy post-chimeric antigen receptor T cell therapy (CART), but limited data exist. We reviewed 14 patients treated with salvage radiation post-CART progression (SRT). Most received SRT for first post-CART relapse (71%) to sites previously PET-avid pre-CART (79%). Median overall survival (OS) post-SRT was 10 months. Post-SRT, six localized relapses achieved 100% response (3 = complete, 3 = partial), with improved freedom from subsequent relapse (P = 0·001) and OS (P = 0·004) compared to advanced stage relapses. Three were bridged to allogeneic transplantation; at analysis, all were alive/NED. SRT has diverse utility and can integrate with novel agents or transplantation to attempt durable remissions.

Role of Radiation Therapy in Patients With Relapsed/Refractory Diffuse Large B-Cell Lymphoma: Guidelines from the International Lymphoma Radiation Oncology Group

Approximately 30% to 40% of patients with diffuse large B-cell lymphoma (DLBCL) will have either primary refractory disease or relapse after chemotherapy. In transplant-eligible patients, those with disease sensitive to salvage chemotherapy will significantly benefit from high-dose therapy with autologous stem cell transplantation. The rationale for considering radiation therapy (RT) for selected patients with relapsed/refractory DLBCL as a part of the salvage program is based on data regarding the patterns of relapse and retrospective series showing improved local control and clinical outcomes for patients who received peritransplant RT. In transplant-ineligible patients, RT can provide effective palliation and, in selected cases, be administered with curative intent if the relapsed/refractory disease is localized. We have reviewed the indications for RT in the setting of relapsed/refractory DLBCL and provided recommendations regarding the optimal timing of RT, dose fractionation scheme, and treatment volume in the context of specific case scenarios.

The role of radiotherapy as salvage and/or consolidation treatment in relapsed/refractory and high-risk diffuse large B-cell lymphoma

OBJECTIVE

Many salvage therapies have been proposed for relapsed/refractory (R/R) diffuse large B-cell lymphomas or for consolidation in the case of suboptimal response. Radiotherapy (RT) is one modality of salvage therapy, but its place is currently not well defined.

METHOD

This study reports a retrospective review of patients receiving unplanned radiotherapy for R/R diffuse large B-cell lymphoma (DLBCL) or primary mediastinal B-cell lymphoma (PMBCL), or as consolidation therapy after second-line chemotherapy, treated in our hospital.

RESULTS

Fifty-one patients with a median age of 53.5 years [19-89] were selected. The histologic type was DLBCL in 35 cases (68%), PMBCL in 8 cases (16%), and secondary transformed NHL in 8 cases (16%). Median aaIPI was 1 [0-4], and 17 patients (33%) had a high tumor burden (bulky disease). Sixteen patients (31%) were irradiated for a response considered to be insufficient, 18 patients (36%) were refractory, and 17 patients (33%) had relapsed. Patients were irradiated with a median dose of 40 Gy [15-44], 29 (57%) by a conformal 3D technique and 22 (43%) by tomotherapy. With a median follow-up of 36 months [1.0-127.8] after irradiation, 5-year progression-free survival (PFS) and overall survival (OS) were 62% and 72%, respectively. In multivariate analysis, adverse factors associated with PFS and OS in our cohort were age >70 years (HR = 5.06, P = .02) and post-RT relapse (HR = 12.24, P = .002), whereas favorable factors were number of lines of chemotherapy <3 (HR = 0.02, P = .03) and bulky disease (HR = 0.02, P = .009).

CONCLUSION

Due to its low toxicity and ease of use, radiotherapy should therefore remain an available option in patients with R/R DLBCL or as consolidation therapy in patients with high-risk disease, mostly in patients with chemo-sensitive disease or bulky disease.