Date Approved

8-11-2026

Graduate Degree Type

Project

Degree Name

Medical Dosimetry (M.S.)

Degree Program

School of Interdisciplinary Health

First Advisor

Kristen Vu

Academic Year

2025/2026

Abstract

Abstract

Purpose

The CHHiP and NRG GU-010 protocols both specify moderately hypofractionated radiotherapy (60Gy in 20fractions) as a radiotherapy option for localized prostate cancer, but differ in target volume definitions, planning target volume (PTV) margins, and organ-at-risk (OAR) dose constraints. This study compares the dosimetric characteristics of CHHiP- and NRG GU-010-based treatment planning to determine whether protocol-specific planning strategies result in meaningful differences in target coverage and normal tissue sparing.

Materials and Methods

Fifteen patients with localized prostate cancer meeting eligibility criteria for both protocols, who were originally planned for the NRG GU-010 protocol, were retrospectively replanned following the CHHiP protocol. All plans were generated using identical beam geometry within the same treatment planning system. Target coverage, dose conformity, maximum dose, and OAR dose-volume metrics were compared.

Results

NRG GU-010 plans resulted in  significantly larger PTV volumes than CHHiP plans (133.0 ± 38.4 cc vs. 76.1 ± 26.8 cc, p < 0.0001). Both techniques achieved excellent target coverage, with mean PTV D95 values exceeding 99%. CHHiP plans demonstrated significantly lower maximum target dose and reduced high-dose exposure to the rectum and bladder. Rectum V60 decreased from 2.94% to 0.80% (p < 0.0001), while bladder V50 decreased from 4.68% to 2.90% (p < 0.0001).

Conclusion

Both planning techniques produced clinically acceptable plans with excellent target coverage. However, the smaller target margins used in the CHHiP protocol resulted in reduced treatment volumes and improved sparing of several normal tissues without compromising target coverage.

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Available for download on Saturday, August 12, 2028

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