Novel Drugs and Radiotherapy in Relapsed Lymphomas: Abscopal Response and Beyond

Combined modality has represented a mainstay of treatment across many lymphoma histologies, given their sensitivity to both multi-agent chemotherapy and intermediate-dose radiotherapy. More recently, several new agents, including immunotherapies, have reshaped the therapeutic panorama of some lymphomas. In parallel, radiotherapy techniques have witnessed substantial improvement, accompanied by a growing understanding that radiation itself comes with an immune-mediated effect. Six decades after a metastatic lesion regression outside the irradiated field was first described, there is increasing evidence that a combination of radiotherapy and immunotherapy could boost an abscopal effect. This review focuses on the mechanisms underlying this interaction in the setting of lymphomas, and on the results of pivotal prospective studies. Furthermore, the available evidence on the concomitant use of radiotherapy and small molecules (i.e., lenalidomide, venetoclax, and ibrutinib), as well as brentuximab vedotin, and chimeric antigen receptor (CAR) T-cell therapy, is summarized. Currently, combining radiotherapy with new agents in patients who are affected by lymphomas appears feasible, particularly as a bridge to anti-CD19 autologous CAR T-cell infusion. However, more studies are required to assess these combinations, and preliminary data suggest only a synergistic rather than a curative effect.

Peritransplant Radiation Therapy in Patients With Refractory or Relapsed Hodgkin Lymphoma Undergoing Autologous Stem Cell Transplant: Long-Term Results of a Retrospective Study of the Fondazione Italiana Linfomi

PURPOSE

In this multicenter collaboration, we report real-world data in the largest published series of long-term outcomes for patients with relapsed/refractory (r/r) Hodgkin lymphoma (HL) treated with peritransplant radiation therapy (pt-RT) and high-dose chemotherapy with autologous stem cell transplant (ASCT).

METHODS AND MATERIALS

We conducted a retrospective analysis including data from 12 institutions. Eligibility required histologic diagnosis of HL, receipt of ASCT plus pt-RT between 2004 and 2014 for r/r HL, and age ≥18 years at the time of ASCT. All patients received salvage chemotherapy for maximum debulking before ASCT. Metabolic responses were scored according to the Lugano Classification. The primary endpoint was overall survival (OS). Univariate and multivariate Cox proportional hazards were calculated to estimate the effect of covariates on patients' outcome.

RESULTS

One hundred thirty-one patients were eligible: 68 were male (52%), and median age at ASCT was 32 years (range, 18-70). At the time of diagnosis with r/r HL, 92 patients (70%) had limited (stage I-II) disease, and 10 patients (8%) had bulky disease. Pt-RT was given pre-ASCT in 32 patients (24%) and post-ASCT in 99 (76%); median prescribed dose was 30.6 Gy (range, 20-44 Gy). With median follow-up of 60 months, 3- and 5-year OS were 84% and 77%, while 3- and 5-year progression-free survival were 75% and 72%, respectively. On univariate and multivariate analysis, advanced stage at relapse (hazard ratio [HR], 2.18; P = .04), irradiation of >3 sites (HR, 3.69; P = .01), and incomplete metabolic response after salvage chemotherapy (HR, 2.24; P = .01) had a negative effect on OS. The sequencing of pt-RT (pre- vs post-ASCT) did not affect outcomes.

CONCLUSIONS

Overall, the addition of pt-RT to ASCT for patients with r/r HL is associated with very good outcomes. Limited relapsed disease with ≤3 sites involved and achievement of complete metabolic response after salvage chemotherapy were predictive of more favorable prognosis.