Robust optimization methods for cardiac sparing in tangential breast IMRT.

Area of Science:

• Radiation Oncology
• Medical Physics
• Image-Guided Therapy

Background:

• Left-sided breast radiotherapy can expose the heart to radiation due to breathing motion.
• Breathing patterns are unpredictable, posing challenges for accurate radiation delivery.
• Protecting the heart is crucial to minimize radiation-induced cardiac toxicity.

Purpose of the Study:

• To evaluate the clinical applicability of a heart-sparing robust optimization approach for breast intensity modulated radiation therapy (IMRT).
• To compare the effectiveness of robust optimized plans against standard clinical plans during free-breathing and deep inspiration breath-hold (DIBH).

Main Methods:

• Utilized 4D-CT scans from eight patients, including two with active breathing control (ABC) for DIBH.
• Generated accumulated dose distributions using deformable registration and simulated breathing patterns.
• Applied robust optimization to minimize heart dose while ensuring target coverage under breathing motion uncertainty.

Main Results:

• Robust optimization plans demonstrated superior or equivalent heart sparing compared to clinical plans.
• Reduced accumulated heart dose (D10cc) by an average of 364 cGy and improved target coverage (D99%) by 477 cGy.
• Showcased significantly smaller deviations between planned and accumulated doses for both heart and target volumes.

Conclusions:

• The robust optimization approach effectively reduces heart radiation dose in free-breathing breast IMRT.
• This method shows potential to decrease reliance on breath-hold techniques for cardiac sparing.
• Clinical implementation of robust optimization can enhance treatment safety and efficacy.