Superiority of equivalent uniform dose (EUD)-based optimization for breast and chest wall

Area of Science:

• Radiation Oncology
• Medical Physics
• Cancer Treatment

Background:

• Intensity-modulated radiation therapy (IMRT) is a standard technique for cancer treatment.
• Optimizing treatment plans involves balancing target coverage with organ at risk (OAR) sparing.
• Traditional dose-volume (DV) objectives may not fully capture the complexity of OAR dose distributions.

Purpose of the Study:

• To compare the dosimetric efficacy of IMRT optimization using generalized equivalent uniform dose (gEUD) objectives versus standard DV-based objectives for OARs.
• To evaluate treatment plans for patients with intact breast and postmastectomy chest wall (CW) cancer.
• To assess if gEUD objectives lead to superior OAR sparing while maintaining target coverage.

Main Methods:

• Four IMRT plans were generated for 10 breast and CW cancer patients: physician-selected DV objectives (phys-plan), gEUD objectives (gEUD-plan), stringent DV objectives (DV-plan), and beam-fluence optimized (FO-plan).
• Dosimetric outcomes were evaluated using metrics like V(20Gy) for the ipsilateral lung and mean dose (Dmean) for the heart, contralateral breast, and contralateral lung.
• The FO-plan served as a benchmark for deliverability without segmentation effects.

Main Results:

• gEUD-based plans demonstrated significantly greater sparing of OARs compared to other methods.
• Average ipsilateral lung V(20Gy) decreased from 22% (FO-plan) to 18% (gEUD-plan).
• All evaluated dosimetric quantities showed a shift towards lower doses with gEUD optimization.

Conclusions:

• gEUD-based IMRT optimization allows for selective dose reduction in OARs, leading to individualized treatment plans.
• This method achieves superior OAR sparing while maintaining equivalent target coverage.
• gEUD optimization provides a valuable tool for developing advanced, patient-specific radiation therapy plans.