For a study, researchers sought to evaluate the robustness of a conventional planning target volume (PTV)-based plan to that of a robust plan to suggest the most robust planning strategy for the target and organ at risk (OAR).

Analysis was done on information from 13 individuals with intermediate- to high-risk localized prostate cancer who did not have T3b disease. A traditional PTV-based plan was used to evaluate the dosage distribution under various setup error situations. For the dosage constraint with the robust plan, the clinical target volume (CTV) and OAR dose in moving coordinates were employed. The dosage limitation of the PTV-rectum was applied to the static coordinate system using the robust hybrid plan. The doses to the CTV, bladder, and rectum of the PTV-based plan, robust plan, and robust hybrid plan were compared when the isocenter was changed by 10 mm superior-inferior, 8 mm right-left, and anterior directions.

Over 95% of the required dosage was secured in all directions for the CTV D99% in the PTV-based and robust hybrid plans, except in the inferior direction. For rectum V70Gy, V60Gy, and V40Gy, there was no discernible difference between the PTV-based and robust hybrid plans. An optimization technique was suggested for patients with prostate cancer in the study.

The dose robustness of the CTV for the robust hybrid plan was greater than that of the PTV-based plan while preserving the equal OAR dosage when the setup mistake occurred within the PTV margin.

Reference: aapm.onlinelibrary.wiley.com/doi/10.1002/acm2.13738