WCLC 2025 - Posters & ePosters-P2.08 .17 Differential Cardiac Dose Evaluation and the Need of Planning Risk Volume (PRV) Margin for the Heart

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This study evaluates the impact of cardiac motion on radiation dose delivery during thoracic radiotherapy and the need for planning risk volume (PRV) margins for the heart. The heart moves continuously due to respiration and intrinsic contractility, shifting downward during inspiration and upward during expiration, causing discrepancies between planned and delivered radiation doses. While 4D CT imaging captures this respiratory motion by providing multiple datasets at various breathing phases, no standardized guidelines exist for selecting the specific CT phase to assess cardiac dose reliably. This leads to uncertainty in dose estimation and challenges in minimizing cardiac exposure during treatment planning.<br /><br />The authors analyzed 54 lung cancer patients with tumors located primarily in the upper lobe and hilar region. Using simulation with 3D and 4D CT scans and volumetric modulated arc therapy (VMAT) planning, they assessed dose variations across different CT datasets including expiration, inspiration, and maximum intensity projection (MIP). They observed significant dose variation attributable to respiratory motion and heart substructure movement, particularly when comparing doses to the atrium versus the ventricle. The study highlights that cardiac substructure-based dose constraints are more reliable than whole-heart volumetric constraints, especially considering lung lobe-specific heart dose variations.<br /><br />Both the results and discussion emphasize the importance of incorporating a PRV margin for the heart (noted at approximately 1 to 3.8 mm depending on substructure and motion) into radiotherapy planning to account for these dose uncertainties. They recommend integrating respiratory phase-specific cardiac dose evaluations in planning for thoracic malignancies to better optimize treatment and reduce cardiac toxicity.<br /><br />In summary, this work advocates for establishing standardized PRV margins and respiratory phase-focused planning protocols, underscoring the necessity of detailed cardiac motion consideration in thoracic radiotherapy to improve cardiac dose accuracy and patient safety.

Asset Subtitle

Karthick Raja M

Meta Tag

Speaker Karthick Raja M

Topic Local-Regional Non-small Cell Lung Cancer

Keywords

cardiac motion

radiation dose delivery

thoracic radiotherapy

planning risk volume (PRV) margins

4D CT imaging

respiratory phase

lung cancer

volumetric modulated arc therapy (VMAT)

cardiac substructures

dose variation