ESTRO 2025 - Abstract Book

S1447

Clinical - Lung

ESTRO 2025

Conclusion: This study introduces the first clinical implementation of adaptive SCINTIX therapy, integrating anatomical and physiological changes into treatment planning. The proposed workflow demonstrates feasibility and clinical value, enabling personalized and precise radiotherapy for cases with significant tumor and PET biodistribution changes.

Keywords: BgRT, Adaptive RT, PET-linac

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Digital Poster Dosimetric and Clinical Predictors of Acute Radiation Pneumonitis in Patients Pre-Treated with Immune Checkpoint Inhibitors Federico Colombo 1 , Marco Galaverni 1 , Cristina Dell'Anna 1 , Elisabetta Lattanzi 1 , Claudia Grondelli 1 , Francesco Salaroli 1 , Ilaria Renna 1 , Giovanni Ceccon 1 , Stella Gianni 1 , Maria Luisa Bergamini 1 , Giulia Mazzaschi 2 , Alessandro Leonetti 2 , Marcello Tiseo 2 , Nicola Sverzellati 3 , Nunziata D'Abbiero 1 , Nicola Simoni 1 1 Radiation Oncology Unit, AOU Parma, Parma, Italy. 2 Medical Oncology Unit, AOU Parma, Parma, Italy. 3 Department of Medicine and Surgery (DiMeC), AOU Parma, Parma, Italy Purpose/Objective: Normal tissue complication probability (NTCP) models for acute radiation pneumonitis (aRP) are largely based on pre immune checkpoint inhibitors (ICIs) data. This study aims to investigate clinical and dosimetric factors influencing the risk of aRP in thoracic radiation therapy (TRT) patients with prior receipt of ICIs. Material/Methods: Patients treated at our Institution with TRT after systemic treatment with ICIs were retrospectively analyzed. Acute events are defined as those occurring within 6 months after TRT and defined as per CTCAE version 5.0. All plans were standardized using equivalent dose in 2 Gy (EQD2) doses. The association between clinical and dosimetric parameters [including mean lung dose (MLD), percentage of normal lungs volume receiving ≥20 Gy (V20), ≥18 Gy (V18), ≥12.5 Gy (V12.5), ≥10 Gy (V10), ≥5 Gy (V5); ipsilateral and contralateral lung MLD, V20, V18, V10, and V5; mean heart dose (MHD), percentage of the heart volume receiving ≥50 Gy, ≥16 Gy (HV50, HV16), dose received by 10% of the heart (HD10)] was evaluated. Results: A total of 69 patients treated from January 2018 to June 2024 were included (table 1). The most common primary malignancy was lung (92.8%). ICIs were PD1 45 (65.2%) or PD-L1 24 (34.8%) inhibitors, administered for a median of 6 cycles (range 1-47) prior TRT. Patients underwent definitive 14 (20.3%), consolidative 34 (49.3%), or palliative 21 (30.4%) TRT, with a median EQD2 dose of 48.8 Gy (range 22.8 – 62.5 Gy). Median PTV and CTV volume were 297 cc (range 37-959 cc) and 73 cc (range 5-575 cc), respectively. aRP occurred in 68.5% of patients, at a median time of 2.5 (range 1.0-7.0 months) months from TRT and was graded G1, G2, G3 and G5 in 32.8%, 23.3%, 8.2%, and 4.1%, respectively. Overall, aRP G≥2 rate was 35.6%, higher than 20% expected according to QUANTEC. Variables associated with any-grade of aRP were lungs V5 (p=0.028), V10 (p=0.039), and MLD (p=0.036); ipsilateral lung V5 (p=0.018), and V10 (p=0.037); and MHD (p=0.009) and HD10 (p=0.003). Variables associated with G≥2 aRP were MHD (p=0.005) and HD10 (p = 0.15), while the variable associated with G≥3 aRP was contralateral MLD (p=0.038). No clinical predictors of aRP were found, including the number of prior ICI cycles or the delivery of concurrent systemic therapy.