ESTRO 2022 - Abstract Book

S153

Abstract book

ESTRO 2022

Figure 1: Cardiac conduction node exposure during mediastinal Hodgkin lymphoma irradiation with volumetric modulated arc therapy (VMAT) or intensity modulated proton therapy (IMPT) with deep-inspiration breath-hold (DIBH). Mean (A) and maximum (B) doses delivered to the heart, to the sino-atrial node (SAN) and to the atrio-ventricular node (AVN). Conclusion The SAN can be substantially exposed during mediastinal HL radiotherapy with DIBH-VMAT. Mean heart dose is poorly representative of conduction node exposure. Proton therapy significantly reduces radiation doses to the cardiac conduction system and might consequently be considered in case of underlying rhythmic or conduction disorders.

PD-0176 Efficacy and safety of total lymphoid irradiation in chronic lung allograft dysfunction phenotypes

A.A.A. Geng Cahuayme 1 , M. Altabas González 2 , M. López Meseguer 3 , M. Vazquez Varela 1 , B. Saez Gimenez 3 , J. Garre Cristau 4 , E. Recalde Vizcay 2 , A. Giraldo Marín 5 , J. Giralt López de Sagredo 6 1 Vall d'Hebron University Hospital, Radiation Oncology , Barcelona, Spain; 2 Vall d'Hebron University Hospital, Radiation Oncology, Barcelona, Spain; 3 Vall d'Hebron University Hospital, Pneumology, Barcelona, Spain; 4 Vall d'Hebron Hospital University , Radiation Oncology, Barcelona, Spain; 5 Vall d'Hebron University Hospital , Radiation Oncology, Barcelona, Spain; 6 Vall d'Hebron University Hospital, Radiation Oncology, Barcelona , Spain Purpose or Objective Describe the efficacy and safety of total lymphoid irradiation (TLI) in a cohort of lung transplant patients with chronic lung allograft dysfunction (CLAD), both bronchiolitis obliterans syndrome (BOS) and restrictive allograft syndrome (RAS) phenotype. Materials and Methods Eligible patients were aged 18 years or old; diagnosed with CLAD and underwent to TLI in our center between June 1 st , 2011 and July 31 st , 2018. CLAD diagnosis and phenotyping were established according to the existing ISHLT Consensus. TLI effects on lung function were assessed for the whole cohort, according to the speed of FEV 1 decline. Patients were followed until redo-transplantation, death or end of study in December 31 st , 2019. Clinical, demographic, and follow-up data were registered. Spirometric follow-up was available in all patients the year before and after TLI. Toxicities were registered according to common terminology criteria for adverse events (CTCAE) version 5.0. TLI was administered in twice a week session of 0.8 Gy, with a targeted total dose of 8 Gy at the clinical target volum e , which involves the low cervical, supraclavicular, infraclavicular, axillary, mediastinal, hilar, paraaortic, iliac, inguinal, and femoral lymph nodes, the spleen and the thymus area with a 3D margin of 1cm. All the patients were treated with 6 and 18 MV photons on Clinac 2100CD linear accelerator with a 3D conformal technique, through 3 isocenters with AP-PA fields in each of them. Results are expressed as frequencies and percentages for qualitative variables and as median (interquartile range) for quantitative variables. Mixed-model regression analysis was used to evaluate changes in FEV 1 during the year before and after TLI. A significant difference in all p-values was considered <0.05. Results A total of 40 LT patients diagnosed with CLAD were treated with TLI in our center. Median time from the diagnosis of CLAD to TLI onset was 4.8 (1.2-48) months. Median follow-up after TLI was 18.1 (1.2 – 97.8) months. TLI treatment led to an attenuation of the FEV 1 decline rate in the whole group. A regression analysis of mixed models is carried out (figure 1). A FEV 1 intercept was 1200 mL/month. We observe that for the entire group prior to TLI there is a significant drop for the entire group of -78.42 ml per month [95% CI -98.16; -58.68 mL/month (p=0.000)]. After the TLI, this drop stabilizes with a monthly gain of 1.6 ml per month during the first year post TLI [95% CI -10.42; 13.72 mL/month (p=0.7889)]. Hematological and gastrointestinal toxicities are described in Table 1. After TLI, severe lymphopenia (toxicity grade 3-4) was present in 22 (57%) patients. In the first 30 days after TLI, 5 (14%) patients had lower respiratory tract infection and one (3%) with an acute diverticulitis (Hinchey Ib). None of them required hospital admission.

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