Publication: Investigation of free breathing technique implication towards cardiac structure dose in left breast radiotherapy: retrospective study
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Date
2025-07
Authors
Shahari, Nur Syahmina
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Abstract
This study aimed to comprehensively evaluate the dosimetric parameters of cardiac structures, assess volumetric-dosimetric correlations, and investigate the relationship between heart dose and LAD specific dosimetry in left breast radiotherapy plans. The objective was to ascertain adherence to recommended tolerance levels and identify critical parameters for cardiac sparing. A retrospective analysis was conducted on 35 left breast cancer patients treated with 3D-CRT at Hospital Pakar Universiti Sains Malaysia (HPUSM) from January to December 2024, receiving a prescribed dose of 40 Gy in 15 fractions. No data beyond December 2024 was included in this study, and the research period did not extend beyond July 2025. Ethical clearance was secured, and purposive sampling was employed. CT simulation was performed under free breathing conditions. Organs at risk (OARs), including the heart, underwent auto-contouring, while the LAD was manually delineated by a medical physicist due to its complicated structure visualized in the CT images. Dosimetric parameters were assessed against RTOG 0617 and DEGRO tolerance guidelines. Spearman's rho correlation analysis was utilized to determine relationships between heart/LAD volumes and their respective doses, as well as between heart mean dose and LAD-specific doses, following preliminary normality testing. The analysis revealed no statistically significant correlation between heart volume and heart mean dose (r =0.018, p=0.917), nor between LAD volume and its dosimetric parameters (LAD Dmean: r =−0.077, p=0.659; LAD V40: r =0.162, p=0.353). A moderate, statistically significant positive correlation was identified between heart mean dose and mean LAD dose (r =0.442, p=0.008). Conversely, the correlation between heart mean dose and LAD V40 (%) was not statistically significant (r =0.240, p=0.165). Volumetric parameters of the heart and LAD do not reliably predict radiation dose to these structures. While a correlation exists between heart mean dose and mean LAD dose, global heart dose metrics are insufficient to fully capture critical high-dose regions within the LAD. Consequently, for effective cardiac sparing in left breast radiotherapy, future planning necessitates meticulous monitoring of both the overall heart mean dose and, crucially, LAD-specific parameters, particularly LAD V40 (%), to ensure comprehensive cardiac protection and mitigate long-term cardiotoxicity. Future investigations should involve larger cohorts to confirm these findings and explore the clinical impact of LAD V40 exceedance.
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