ESTRO 2020 Abstract Book

S487 ESTRO 2020

Purpose or Objective The role of salvage radiotherapy in patients with relapsed/ refractory (r/r) Diffuse Large B-Cell Lymphoma (DLBCL) is unclear in the rituximab era. We sought to determine the efficacy and toxicity of radiotherapy for this group of patients. Material and Methods We searched MEDLINE and various conference proceedings for eligible studies where patients were treated with salvage radiotherapy for r/r DLBCL, excluding patients that received consolidation radiotherapy as first line treatment. Outcomes of interest were 2 and 5-year overall survival (OS-2, OS-5), 2 and 5-year freedom from progression (FFP-2, FFP-5) and Grade 3 or 4 adverse events (AE). We used random effects model to pool outcomes across studies and compared pre-defined subgroups using interaction test. Results We found 13 eligible non-comparative studies with methodological limitations identified. The studies included 412 patients who received rituximab based chemotherapy as first-line treatment. Of these, 2 were of a prospective design, 3 studies used peri-stem cell transplant radiotherapy, and 3 involved radiotherapy to primary mediastinal lymphoma. We found that salvage radiotherapy was associated with a OS-2 rate of 94% (95% confidence interval (CI) 84 – 95%, I 2 = 55%), OS-5 rate of 83% (95% CI 76 – 89%, I 2 = 64%), FFP-2 rate of 81% (95% CI 72 - 90%, I 2 =74%), FFP-5 rate of 74% (95% CI 65 -82%, I 2 = 74%), and Grade 3 or 4 AE rate of 8% (95% CI 2 -14%, I 2 = 0%). Sub-group analysis showed that studies with prospective design had higher rates of OS-2 and OS-5 compared with studies of retrospective design (OS-2: 97% versus (vs) 81%, interaction P (IP) = 0.009; OS-5: 95% vs 75%, IP = 0.003) and studies which employed peri-stem cell transplant RT had lower rates of OS-5 compared to studies without stem cell transplant (59% vs 73%, IP = 0.02). Conclusion The meta-analysis provides evidence to suggest that salvage radiotherapy results in encouraging disease control and survival rates. The level of evidence was low emphasizing the need for high quality randomized trials to establish the optimal management strategy for r/r DLBCL. PO-0913 Effectiveness of radiotherapy for patients with indolent non-Hodgkin's lymphoma I. Hadi 1 , A. Schummer 1 , C. Eze 1 , M. Dreyling 2 , C. Belka 1 , M. Li 1 1 University Hospital LMU, Department of Radiation Oncology, Munich, Germany ; 2 University Hospital LMU, Department of Oncology, Munich, Germany Purpose or Objective Radiotherapy is a mainstay of lymphoma therapy. We analyzed the results of patients with indolent non- Hodgkin's lymphoma (iNHL), who were treated with radiation in our clinic, retrospectively. Material and Methods Patients with iNHL treated between 1999 and 2016 were included. The primary endpoint of this study was progression-free survival (PFS). Secondary endpoints were local control (LC), toxicity and overall survival (OS). PFS, LC, and OS were analyzed using the Kaplan-Meier method. The log-rank test was used to investigate the differences between subgroups. The Cox proportional hazard model was used for univariate continuous analysis. Results Ninety patients were analyzed retrospectively. The median follow-up was 74 months (2-227 months). Stage I after Ann-Arbor was observed in 66 (73.3%), stage II in 19 (21.1%), stage III in 4 patients (4.4%), and stage IV in 1 patient (1.1%). Patients were treated with a median single dose of 2.0 Gy (range: 1.5-2.0 Gy) and a median total dose of 36.0 Gy (range: 16.0-60.0 Gy). Radiotherapy was performed in 2D (n = 17; 18.9%), 3D (n = 70; 77.8%) and

Policlinico San Martino, Medical Physics, Genova, Italy ; 4 Università degli Studi di Genova, Radiation Oncology, Genova, Italy ; 5 Università degli Studi di Genova, Hematology, Genova, Italy Purpose or Objective Salvage chemotherapy followed by autologous stem cell transplantation (ASCT) is the standard of care for patients with relapsed/refractory (R/R) lymphomas. Involved site radiotherapy (ISRT) showed a potential benefit before or after ASCT in Hodgkin disease (HL). Data about the efficacy of ISRT and ASCT in non-Hodgkin lymphomas (NHL) are lacking. In ASCT plus ISRT, progression and relapse are lower if radiotherapy is performed over all the disease sites that emerged from the diagnosis (Wirth 2019). Total Body Irradiation is a viable alternative to chemotherapy in the conditioning regimen for NHL (Tseng 2018). This suggestion reinforces the potential role of large fields as total lymphoid irradiation (TLI) in R/R patients with an advanced stage of disease at diagnosis. Hyperfractionated TLI, before ASCT, has already shown promising results in advanced HL (Evans 2007; Gentzler 2014; Rimmer 2017). Our study aimed to assess the feasibility of TLI, delivered with an hypofractionated schedule by helical tomotherapy, followed by high dose chemotherapy (HDCT) for ASCT in R/R NHL and HL. Material and Methods From February 2011 to December 2018, 20 patients with R/R HL (n=7), Diffuse Large B Cell NHL (n=11) and T-cell NHL (n=2) were treated. The median age was 42 years (range 20-68) and median previous lines of therapy were 3 (range 2-4). All the NHL were minimum stage III at diagnosis. Four patients had already received prior ASCT. The TLI total dose of 12 Gy was delivered in a daily fraction of 4 Gy for 3 consecutive days. HDCT was administered 4 days later. Conditioning chemotherapy consisted of high- dose Bendamustine (400 mg/sqm) and Melphalan 140 (mg/sqm) for patients older than 40 years (n=10) and conventional FEAM (Fotemustine, Ethoposide, Cytarabine and Melphalan) for younger patients. Results Salvage chemotherapy-induced CR in 9 patients (5 HL, 4 NHL), PR in 5 (2 HL, 3 NHL), less than PR in 6. Eight patients (40%) experienced fever of unknown origin and 8 patients (40%) developed grade 3/4 mucositis. None experienced other grades 3/4 extra-hematological toxicity. The median number of CD34+ cells infused was 5,5 x 106/kg (range 2,1 -11,6). All patients showed complete engraftment, the median time to neutrophil and platelet recovery was 11 (range 9-21) and 12.5 days (range 9-21) respectively. Median follow-up was 64.9 months (CI 95% 22.5-107.3 months). All patients in PR or less before transplant achieved CR. No cases of treatment-related death were recorded. The 3-year overall PFS and OS were 55.5% and 72.8% (Fig) respectively. Post-ASCT relapse occurred in 9 patients (HL=2 and NHL=7) at a median time of 8 months. Conclusion Our preliminary results show that 4 Gy daily TLI is safe in advanced NHL and HL. With the limit deriving from the small size of this series, we observe that all patients achieved CR after the procedure, and that the relapse rate was relatively low, altough the total radiation dose was low. All the imaging is under centralized revision to identify potential bias. PO-0912 Role of salvage radiotherapy in relapsed/ refractory DLBCL in the rituximab era: A meta-analysis F. KazmI 1 , B. Vellayappan 2 , Y. Kheng Wei 3 , I. Sin Huili 3 , B. Fei Tan 3 , S. Poh Shuxian 3 1 Churchill Hospital, Oncology, Oxford, United Kingdom ; 2 National University Hospital Singapore, Radiation Oncology, Singapore, Singapore ; 3 National Cancer Centre Singapore, Radiation Oncology, Singapore, Singapore