why choose us

300×250 Ad Slot

Research Article: Comparative dosimetric and radiobiological assessment of a hybrid-VMAT strategy incorporating supplemental short-arcs for left-sided postmastectomy radiotherapy

Date Published: 2026-05-19

Abstract:
Postmastectomy radiotherapy (PMRT) for left-sided breast cancer poses persistent dosimetric challenges due to the complex target geometry and its proximity to critical organs at risk (OARs), particularly the heart and the left anterior descending (LAD) coronary artery. This study evaluated the dosimetric and radiobiological performance of a volumetric modulated arc therapy (VMAT) approach incorporating a supplemental short-arc segment, comparing it against conventional IMRT and standard VMAT strategies. Thirty-six left-sided breast cancer patients undergoing PMRT were retrospectively replanned using six techniques: 5-field and 7-field IMRT, tangential half-arc and wide-arc VMAT (THVP, TWVP), and two modified VMAT plans augmented with a 40° short-arc segment (sub-THVP, sub-TWVP) designed for coronary sparing. Plan quality was assessed via dose-volume histogram (DVH) metrics. Radiobiological evaluation included Normal Tissue Complication Probability (NTCP) via the Lyman-Kutcher-Burman and Poisson-LQ models, alongside secondary cancer risk (EAR/ERR) quantification using the full mechanistic Schneider OED model. All VMAT-based techniques significantly improved target conformity and homogeneity over IMRT (p< 0.001). Among all evaluated strategies, sub-TWVP achieved the optimal trade-off between target coverage and cardiopulmonary sparing. It yielded the lowest ipsilateral lung exposure (V 5Gy : 44.86%, V 20Gy : 20.50%, D mean : 11.37Gy). Crucially, the short-arc integration in sub-TWVP significantly reduced cardiac exposure relative to standard TWVP, lowering heart V 5Gy and V 30Gy by 29.1% and 25.2% (p< 0.05), respectively, while achieving the lowest LAD D mean (17.84 Gy). Radiobiologically, sub-TWVP yielded the lowest NTCP for the ipsilateral lung (0.045%) and minimized cardiac toxicity risks (0.16% for pericarditis, 0.36% for cardiac mortality). Furthermore, while standard VMAT inherently increased the low-dose bath to the contralateral lung compared to IMRT, the short-arc strategies subtly mitigated the corresponding modeled secondary cancer risk relative to their standard VMAT counterparts. Incorporating a 40° supplemental short-arc into tangential VMAT—particularly within a wide-arc configuration—significantly enhances cardiac and LAD sparing while preserving VMAT’s superior target coverage. Integrating complementary radiobiological modeling with DVH metrics provides critical insights for optimizing technique selection, effectively balancing normal-tissue toxicity against secondary cancer risks.

Introduction:
Breast cancer is the most commonly diagnosed malignancy and a leading cause of cancer-related mortality in women worldwide ( 1 ). Approximately 2.3 million new cases are diagnosed annually, with roughly 670,000 deaths attributed to the disease ( 2 ). For patients presenting with high-risk pathological features or locally advanced disease, modified radical mastectomy followed by adjuvant postmastectomy radiotherapy (PMRT) constitutes a cornerstone of multidisciplinary management, significantly reducing locoregional…

Read more

300×250 Ad Slot