ESTRO 2024 - Abstract Book

S1695

Clinical - Lung

ESTRO 2024

2. M. Savanović et al.(2022): Assessment of Organ Dose Reduction Using Dynamic Conformal Arc and Static Field with FFF Beams for SBRT in Lung Cancer, Cancer Investigation.

3. Kim S-T et al. Non-coplanar VMAT plans for lung SABR to reduce dose to the heart: a planning study. Br J Radiol 2020; 93.

4. Marrazzo L et al. Automated planning through robust templates and multicriterial optimization for lung VMAT SBRT of lung lesions. J Appl Clin Med Phys. 2020; 21: 114-120.

1787

Digital Poster

MR-guided stereotactic ablative radiotherapy for central lung tumors: long-term clinical outcomes.

Hilâl Tekatli, Nicolas Giraud, Miguel A. Palacios, John R. van Sornsen de Koste, Cornelis J.A. Haasbeek, Famke L. Schneiders, Suresh Senan

Amsterdam UMC, Radiation Oncology, Amsterdam, Netherlands

Purpose/Objective:

Stereotactic ablative radiotherapy (SABR) for central lung tumors is associated with increased rates of bronchial stenosis and fatal hemoptysis. Tumor proximity to major airways has been identified as a risk factor for toxicity. Delivery of breath-hold MR-guided adaptive SABR (MR-SABR) using automatic beam gating allows for smaller PTV margins, which improves normal organ sparing. We studied the long-term clinical outcomes after MR-SABR for central lung tumors.

Material/Methods:

Central lung tumors were defined using IASLC criteria. All patients treated at a single institution between 2016-2022 were identified in our ethics-approved MR-SABR database. Treatments were simulated on a 0.35 T MR scanner with a true FISP sequence acquisition using a breath-hold 3D MR. GTV contours were generated on a breath-hold planning CT scan, and subsequently co-registered on the 3D MR scan by the same clinician. SABR plans were generated using step-and-shoot IMRT beams and normalized to cover 95% of the PTV by the prescription dose. On table editing of contours was only performed if considered clinically relevant. The PTV margin used was 5 mm for patients treated on the MR-linac; early cases treated on an MR-cobalt unit utilized a 3 mm margin. SABR was delivered in repeated breath-holds under continuous visualization of the tracked GTV in a sagittal MR plane. Median follow-up times were calculated with the reverse Kaplan-Meier method and the time-to-event outcomes were calculated with the Kaplan-Meier method.

Results: