Authors: Robert Inshetski, MS, CMD, RT(R)(CT)(T), Nishele Lenards, PhD, CMD, RT(R)(T), FAAMD, Ashley Hunzeker, MS, CMD

Medical Dosimetry Program at the University of Wisconsin-La Crosse, WI, USA

Abstract:
Many radiation planning techniques have been used to increase dose to the vulvar surface when treating patients with vulvar cancer with volumetric modulated arc therapy. Target volumes near the skin surface, such as vulvar tumors, do not meet the International Commission on Radiation Units and Measurements safety guidelines. Without the needed expansions and setup uncertainties, there are concerns that treated dose to the vulvar surface varies from the planned dose. The purpose of this study was to determine if the robust optimization tool used in volumetric modulated arc therapy planning can reproducibly deliver prescription dose to the vulvar skin surface despite setup uncertainties and reduced safety margins. To further mitigate the possibilities of setup errors and dose variation to the vulvar surface, robust optimization during planning must be considered. For this case study, 5 patients with similar diagnoses and vulvar surface dose requirements were retrospectively replanned using robust optimization. An evaluation structure was created representing the vulvar surface for each patient. This structure was assigned robustness characteristics. After multiple optimizations and planning scenarios, perturbed dose representing dataset shifts were evaluated along the vulvar surface. Every patient met minimal metrics of 100% of vulvar sur- face volume receiving 95% of the prescription dose. An additional review of 95% of vulvar surface volume receiving 100% of the prescription dose showed similar results. Robust optimization can be used in the planning process to mitigate setup uncertainties.

As of January 1, 2022, ARRT requires CE Credits for Directed Journal Readings to be based on the word count for each article. So, the number of CE Credits for each DJR article will vary for ARRT. For this article, the ARRT CE Credit will be 1 Credit. The MDCB CE Credits will remain at 2.5 Credits.

ARRT CQR Credit Distribution
Radiation Therapy 2017:
Procedures
     Prescription and Dose Calculation = 1.00 credits
Radiation Therapy 2022:
Procedures
     Prescription and Dose Calculation = 1.00 credits