ESTRO 2021 Abstract Book

S897

ESTRO 2021

Conclusion HDR brachytherapy is a useful technique for treating complex surfaces involved with cutaneous lymphoma with a very high response rate, improved local relapse rate, minimal toxicities and reduced dose to normal tissues. PO-1079 Do you use RT as part of bridging therapy for the treatment of DLBCL with CAR-T cells? C. Prieto Prieto 1 , S. Sequero López 2 1 San Cecilio Clinical University Hospital, Radiation Oncology, Granada, Spain; 2 San Cecilio Clinical University Hospital, Medical Oncology, Granada, Spain Purpose or Objective Disclose the success of concomitant use of chemo and targeted therapies with involved site radiotherapy (ISRT) as intensive bridging therapy in a case of refractory cervical DLBCL subsequently undergoing CAR-T cell infusion. Materials and Methods We present the case of a female patient with a history of gastric follicular lymphoma treated six years ago, who presented a relapse with malignant transformation of cervical LBDCG refractory to chemotherapy. Up to 3 lines of different systemic therapies (R-ESHAP, R-MINE, R-GEMOX) were used to control tumor growth but a sustained response was not achieved, so autologous transplantation could not be performed. Given the refractory disease, the patient was considered as a candidate for CAR-T cell therapy. Within the second week of treatment with R-GEMOX, the tumor presented an aggressive biological growing causing dysphagia, pain, cough, facial deformity and high risk of airway obstruction. Once the lymphocyte apheresis for the CAR-T cell preparation was done, we decided to use an intensive bridge therapy based on Polatuzumab + Bendamustine + Rituximab in concomitance with radiotherapy. A total dose of 40Gy at 2Gy per fraction of ISRT was administered, planned with VMAT. Finally, the infusion of CAR-T cell was performed some weeks later thanks to the great clinical response obtained. Results A complete clinical response was obtained throughout the week after the end of the treatment. It was possible to avoid the obstruction of the airway and complete the CAR-T cell procedure. Tolerance was moderate during the treatment. The patient required hospitalization due to febrile pancytopenia with grade-2 mucositis and dysphagia. However she recovered from the clinical and hematological toxicity during the following month. More ahead, she had a self-limited episode of pain in the tooth next to the radiation field, with no apparent triggering cause, which required a visit to the dentist. Nowadays, she is being reviewed in our departments for plaquetopenia as chronic secondary effect after CAR T cell therapy. No radiation induced late toxicities (cervical skin induration, xerostomia) are referred by the patient. Conclusion According to retrospective studies, bridging therapy is required in 69% of cases, but RT is used in only 15% of them. There is a strong rationale to use of RT as local treatment because most of relapses are located at the original site, RT reduces relapse rate by 20%, and it may augment an immune response sensitizing antigen negative cells to CAR-mediated death. In this case report, we show a very good clinical response including RT with the use of biological targets or chemotherapy. It might increase tumor radiosensitivity, but also acute toxicity; although it is acceptably tolerated. This combination should be included in future studies in order to establish the optimal schedule for bridge therapy in CART cell.