Graduate Degree Type
Medical Dosimetry (M.S.)
Prostate cancer is one of the most common cancers among men, and its incidence is a significant health concern. The optimal radiation treatment for prostate cancer patients needs to be tailored to reduce toxicities to organs at risk within the treated area. This study aims to retrospectively evaluate the dose distribution to organs at risk (OARs) in patients with hip prosthetics for volumetric modulated arc therapy (VMAT) prostate cancer plans.
The study included ten prostate cancer patients with at least one prosthetic hip who received VMAT plans at a Midwest Radiation Oncology Center. Various data points, including target volume (PTV) coverage and OAR doses, were collected and analyzed. The study compared VMAT prostate plans with optimal dose avoidance structures (avoidance plans) to plans without dose avoidance structures when prosthetics were overridden to water (override plans).
The study found that override plans resulted in cooler PTV doses than avoidance plans, as indicated by the negative Rank Biserial Correlation (RBC) values for hot spot (Hs) and D2. However, statistical significance was observed only for Hs and D2, indicating lower doses in the override plans. Within OARs the rectum V52.8 data point showed statistical evidence that override plans had lower doses than avoidance plans, with a mean decrease of 1.6% for V52.8. However, the conclusion of data would not indicate a clinical significance as all plans were still meeting constraints set by the physician to prevent side effects associated with the rectum.
The study found little statistically significant evidence to support the hypothesis that VMAT prostate plans with optimal dose avoidance structures deliver higher doses to OARs than plans without dose avoidance structures when prosthetics are overridden to water. While there were some differences in dose distribution, they were not clinically significant. The research highlights the importance of considering optimal dose avoidance structures for prostate cancer patients with hip prosthetics to minimize side effects. Further studies with larger patient populations and different treatment energies are warranted to validate these findings.
Brinkman, Jared Richard, "A Retrospective Comparison of Dose Distribution within Density Override and Avoidance Structures in Volumetric Arc Therapy Prostate Plans with Hip Prosthetics: A Dosimetric Evaluation" (2023). Culminating Experience Projects. 368.