Identifier

etd-06062016-160049

Degree

Master of Science (MS)

Department

Physics and Astronomy

Document Type

Thesis

Abstract

Purpose: To determine if bolus electron conformal therapy (BECT) combined with volumetric modulated arc therapy (VMAT) and flattening filter free volumetric modulated arc therapy (FFFVMAT (6x and 10x)) can maintain equal or better dose coverage than standard volumetric modulated arc therapy (VMAT) while reducing doses to organs at risk (OARs). Methods: BECT+VMAT, FFFVMAT (6x and 10x), and VMAT treatment plans were produced for ten post-mastectomy radiotherapy (PMRT) patients previously treated at our clinic. The treatment plans were created on a commercially available treatment planning system (TPS) and all completed treatment plans were reviewed and approved by a radiation oncologist. The plans were evaluated based on planning target volume (PTV) coverage, tumor control probability (TCP), dose homogeneity index (DHI), conformity index (CI), dose to organs at risk (OARs), and second risks for OARs. Results: All techniques produced clinically acceptable PMRT plans. Overall, BECT+VMAT plans exhibited significantly higher maximum dose compared to all VMAT techniques. BECT+VMAT and FFFVMAT10x had slightly improved TCP over FFFVMAT6x and VMAT (p > 0.05). However, all VMAT techniques showed statistically significant improvement in CI and DHI over BECT+VMAT. All techniques showed no statistical significant difference in mean lung dose. BECT+VMAT exhibited a reduced mean heart dose over VMAT (p = 0.06). FFFVMAT6x had significantly higher mean heart dose compared to VMAT. In addition, BECT+VMAT was able to reduce mean dose to the contralateral breast with statistical significance, compared to VMAT. Both FFFVMAT techniques had comparable but slightly reduced dose compared to VMAT with FFFVMAT6x showing statistical significance. Conclusion: This work has shown that BECT+VMAT produces clinically acceptable plans while reducing OARs doses. Both FFFVMAT techniques are comparable to VMAT with FFFVMAT6x having slight improvements. In addition, FFFVMAT techniques exhibited reduced treatment times over VMAT. Even though all VMAT techniques produce more homogenous and conformal dose distributions, BECT+VMAT is a viable option for treating post-mastectomy patients. This work has demonstrated that patients with increased risk of cardiovascular disease or radiation-induced cancer of the contralateral breast may benefit from BECT+VMAT. Also, patients with increased risk of radiation-induced cancer of the contralateral breast may benefit from FFFVMAT6x.

Date

2016

Document Availability at the Time of Submission

Secure the entire work for patent and/or proprietary purposes for a period of one year. Student has submitted appropriate documentation which states: During this period the copyright owner also agrees not to exercise her/his ownership rights, including public use in works, without prior authorization from LSU. At the end of the one year period, either we or LSU may request an automatic extension for one additional year. At the end of the one year secure period (or its extension, if such is requested), the work will be released for access worldwide.

Committee Chair

Zhang, Rui

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