ESTRO 2022 - Abstract Book

S996

Abstract book

ESTRO 2022

1 Santa Maria della Misericordia Hospital, Section of Radiation Oncology;, Perugia, Italy; 2 University of Perugia, Department of Hematology;, Perugia, Italy; 3 University of Perugia, Department of Hematology;, Perugia, Italy; 4 University of Perugia, Department of Radiation Oncology,, Perugia, Italy; 5 Santa Maria della Misericordia Hospital, Medical Physics Section, Perugia, Italy; 6 Santa Maria della Misericordia Hospital, Santa Maria della Misericordia Hospital, Perugia, Italy; 7 University of Perugia, Department of Radiation Oncology,, Perugia, Italy; 8 University of Perugia, Department of Hematology;, per, Italy Purpose or Objective Chimeric antigen receptor (CAR) T-cells are autologous genetically engineered T cells recognizing tumor surface antigens. CAR-T cell targeting CD19 antigen has transformed salvage approach in relapsed/refractory B-cell lymphomas, achieving high response rates and durable remissions. However, several issues still need to be resolved to further optimize outcomes. One this challenges is to identify the optimal therapeutic regimen to maintain disease control prior to infusion of anti-CD19 CAR T-cells, during the 4 weeks period of product manufacturing (so called bridging therapy). In this context, radiation therapy (RT) may be a valuable bridging therapy to CAR T-cell therapy, offering tumor control and reduced toxicity, especially when disease burden is limited. Preliminary data from retrospective analysis showed early evidence that RT can be safe and effective as a bridging treatment. Therefore, RT may have complementary immunomodulatory activity with CAR-T cells. Here we describe a case series of our patients affected by high grade non Hodgkin Lymphoma, receiving radiation as a bridge therapy to anti-CD19 CAR T-cells. Materials and Methods Between August 2020 and July 2021, 7 patient (3 M, 4 F) received bridging radiation before antiCD19 CAR T-cells. Median age was 47 years (25-69). Patient were affected by Diffuse Large B cell Lymphoma relapsed and/or refractory to chemotherapy and autologous stem cell transplantation, with a median of 5 lines of prior therapy (2-12). All patients received 2 to 2.5 Gy/fraction to a median dose of 32.4 Gy (20-42) with extended field RT surrounding disease involvement. One patient received concurrent chemotherapy. Median time from the end of RT to CAR-T cell infusion was 39 day(16-66). Results After the end of RT and before CAR-T cell infusion, 3/7 patient experienced haematological toxicities (1 grade III pancytopenia; 1 grade IV pancytopenia in the patient treated with concomitant chemotherapy), while 4/7 patients showed no significant toxicities. Disease assessment by PET-CT after RT in 6/7 patient, showed 5 complete remissions and 1 stable disease. At a median follow-up was 7.8 months (2–12) after CAR-T cell therapy, all patient are in complete remission. Conclusion RT can be considered as a safe and effective bridge approach to CAR-T cell therapy in patient affected by Diffuse Large B cell Lymphoma. Future investigation is warranted to optimize timing and dose of bridging radiation before CAR T therapy. 1 Centre Georges François Leclerc, Radiotherapy department, Dijon, France; 2 Centre Georges François Leclerc, Medical physics department, Dijon, France Purpose or Objective Evaluation of the efficiency of a 3D surface imaging compared to “lasers and skin marks” modality for prepositioning, in term of accuracy and time required, concerning patients treated by adjuvant Volumetric Modulated Arc Therapy (VMAT) radiotherapy for a breast cancer. Materials and Methods 40 patients, retrospectively included, were prepositioned with “laser and skin marks” method and were compared to 51 patients, prospectively included, and prepositioned with AlignRT (Vision RT, London, UK). A daily Cone Beam Computed Tomography (CBCT) has been acquired to reposition each patient at each fraction. Regarding the accuracy, shifts values were analyzed for the six degrees of freedom, with absolute values for the first session and normalized values for all sessions. Indeed, shifts values analyzed were the residual set-up errors after the acquisition of the CBCT. To evaluate the time needed to position, prepositioning time (defined as the time between the plan opening on the linac and the acquisition of the first CBCT) and positioning time (defined as the time between the plan opening on the linac and the beginning of the first treatment beam) were analyzed. Results Through all sessions, pitch, longitudinal and lateral shifts were significantly lower while yaw and vertical shifts were significantly higher with the AlignRT system compared to “lasers and skin marks”. There was no significant difference between the two cohorts for roll shifts. Every residual set-up error was < 0.5cm or < 1° for both cohorts. At the first session, prepositioning time and positioning time were longer with AlignRT compared to “lasers and skin marks”, but there was no significant difference for positioning time and prepositioning time regarding all sessions. There would even be a significant lower positioning time with AlignRT if only unilateral locations are considered. Conclusion AlignRT and “lasers and skin marks» methods are consistent towards translation and rotation shifts. However, AlignRT present a lower positioning time than “lasers and skin marks” for unilateral location. In addition, AlignRT offers the Poster (digital): Breast PO-1175 Prepositioning evaluation of breast/chest wall patient: surface guided versus lasers and skin marks C. Nicolet 1 , L. Delcoudert 2 , L. Aubignac 2 , K. Peignaux 1 , M. Gonod 2