Reducing Heart Dose with Protons and Cardiac Substructure Sparing for Mediastinal Lymphoma Treatment

Area of Science:

• Radiation Oncology
• Medical Physics
• Cardiology

Background:

• Intensity modulated radiation therapy (IMRT) with cardiac substructure sparing (CSS) optimization aims to reduce radiation dose to cardiac substructures.
• Electrocardiogram-gated computed tomography angiography is utilized for precise treatment planning in IMRT.
• Mediastinal lymphoma patients are at risk of cardiac toxicity due to radiation therapy.

Purpose of the Study:

• To investigate if intensity modulated proton therapy (IMPT) can further reduce radiation dose to cardiac substructures compared to IMRT in mediastinal lymphoma patients.
• To evaluate the effectiveness of IMPT in cardiac substructure sparing (CSS) optimization.

Main Methods:

• Twenty-one patients with mediastinal lymphoma underwent electrocardiogram-gated computed tomography angiography for radiotherapy planning.
• Comparative treatment planning was performed using both IMPT and IMRT for 13 patients with delineated cardiac substructures.
• Plans were normalized for equivalent 95% target volume coverage to ensure a fair comparison.

Main Results:

• IMPT-CSS significantly reduced mean dose to all cardiac substructures, including coronary arteries and cardiac valves, compared to IMRT-CSS.
• Average whole-heart dose was reduced from 9.6 Gy to 4.9 Gy with IMPT (P < .0001).
• Clinically meaningful improvements were observed in coronary arteries (69%), cardiac valves (77%), and the whole heart (100%) with IMPT.

Conclusions:

• IMPT-CSS treatment planning significantly reduces radiation dose to cardiac substructures in patients with mediastinal lymphoma.
• The observed dose reductions suggest potential for improved clinical outcomes, aligning with previous CSS optimization analyses.
• IMPT represents a promising advancement for reducing cardiac toxicity in mediastinal lymphoma radiotherapy.