Novel adaptive beam-dependent margins for additional OAR sparing

Area of Science:

• Radiation Oncology
• Medical Physics
• Radiotherapy Treatment Planning

Background:

• Margins in radiotherapy are crucial for covering the clinical target volume (CTV) despite geometric uncertainties.
• Standard margins can inadvertently increase radiation dose to surrounding organs at risk (OARs).

Purpose of the Study:

• To propose and investigate a novel adaptive margin concept for radiotherapy treatment planning.
• To assess the impact of adaptive margins on OAR sparing and CTV dose coverage in prostate cancer.
• To compare adaptive margins with standard beam-dependent margins.

Main Methods:

• Developed an adaptive margin concept that molds away from selected OARs.
• Applied the adaptive margin concept to prostate radiotherapy treatment plans for five patients.
• Compared plans using standard beam-dependent margins versus adaptive margins (rectum, rectum and bladder).

Main Results:

• All plans achieved comparable CTV dose coverage probability (90% population coverage, 95% prescribed dose).
• Adaptive margins significantly improved high-dose sparing for considered OARs (rectum, bladder).
• The degree of OAR sparing depended on the number of OARs adapted and their proximity to the CTV.

Conclusions:

• The adaptive margin concept offers improved OAR sparing in prostate radiotherapy without compromising CTV dose coverage.
• This approach provides a promising strategy for optimizing radiotherapy plans by selectively reducing dose to critical structures.
• Further investigation is warranted to explore the broader applicability and potential trade-offs of adaptive margins.