Date Approved

8-10-2026

Graduate Degree Type

Project

Degree Name

Medical Dosimetry (M.S.)

Degree Program

School of Interdisciplinary Health

First Advisor

Daniel Pham

Second Advisor

Bethany Marshall

Academic Year

2025/2026

Abstract

Normal tissue toxicity is an essential consideration in the development of robust radiotherapy plans. Thoracic radiation has been closely linked to cardiac morbidity and mortality, with increasing focus given to the amount of dose specific substructures of the heart receive. In mid- to distal esophageal cancers specifically, the left anterior descending (LAD) coronary artery falls in close proximity to treatment targets, creating potential concern for radiation related-related cardiac toxicity. This study aimed to evaluate the effectiveness of three dose-limiting treatment planning strategies – dose fall-off (DFO), equivalent uniform dose (EUD), and treat-and-protect (TxP) – for reducing dose to the LAD in volumetric- modulated arc therapy plans for esophageal cancer. A retrospective plan comparison was performed using anonymized datasets from ten patients previously treated for mid- to distal esophageal cancer, using standard fractionation scheme (50.4 Gy in 28 fractions). The original clinical plan was duplicated into three intervention plans, with each plan incorporating a different planning strategy and subsequently re-optimized to maintain 95% coverage of the to the planning target volumes (PTVs). Dose distributions to organs at risk (OARs) were then evaluated and statistically analyzed. All three planning techniques successfully reduced dose to the LAD while maintaining target coverage. However, lung mean dose and V20 significantly increased with the addition of LAD dose-limiting optimization strategies, but not to the extent of being clinically significant.

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