Date Approved

7-28-2022

Graduate Degree Type

Project

Degree Name

Medical Dosimetry (M.S.)

Degree Program

Health Professions

First Advisor

Kristen Vu

Academic Year

2021/2022

Abstract

Introduction

Post mastectomy radiation therapy can cause significant skin reaction for patients treated with bolus. The elimination of bolus as a standard practice for this treatment has been suggested in recent literature. Additionally, volumetric modulated arc therapy (VMAT) may deliver a comparable plan with the benefit of reducing treatment times for this population compared to static field intensity modulated radiation therapy (IMRT).

Methods

This study is a retrospective dosimetric analysis of ten right-sided postmastectomy radiation therapy patients. The subjects had previously completed a course of radiation therapy consisting of static field IMRT with the use of bolus every other day (qod). The researcher used the same data set and planning objectives to create two VMAT plans. One VMAT plan consisted of continuous arcs, while the other consisted of partial arcs with predefined avoidance sectors. Each VMAT plan was created without the use of bolus.

Results

Numeric data was collected, and statistical analysis was performed. Non-parametric Wilcoxson Signed Ranks tests were completed to compare difference in means between IMRT qod bolus and both VMAT full arc and VMAT partial arc. Results are given for planning target volumes, organs at risk, and a skin rind contour.

Conclusion

Static field IMRT qod bolus and VMAT no bolus plans have comparable dosimetric results. Of clinical significance is that all plans met clinical goals. Skin dose was found to be less in VMAT plans with a statistically significant difference compared to IMRT qod bolus. Nonetheless, skin dose was found to be of an appropriate dose for decrease in toxicity and comparable local control.

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