Can protons improve SBRT for lung lesions? Dosimetric considerations

Area of Science:

• Radiation Oncology
• Medical Physics

Background:

• Hypofractionated stereotactic body radiotherapy (SBRT) is an advanced cancer treatment.
• Proton therapy offers potential advantages over traditional photon therapy due to its physical properties.

Purpose of the Study:

• To investigate the dosimetric benefits of proton therapy (PT) and intensity modulated proton therapy (IMPT) compared to 3D conformal photon therapy (3D-CRT).
• To evaluate these techniques under different breathing conditions for SBRT of lung lesions.

Main Methods:

• Retrospective analysis of 12 patients undergoing hypofractionated SBRT (3x15Gy).
• Comparison of passively scattered protons (PT), intensity modulated proton therapy (IMPT), and 3D-CRT.
• Evaluation of shallow breathing with abdominal compression (SB+AC) versus deep inspiration breath hold (DIBH) techniques.
• Dosimetric analysis of planning target volume (PTV), lung, heart, and esophagus using dose-volume histograms (DVH).

Main Results:

• Proton techniques (PT and IMPT) demonstrated superior sparing of the heart and contralateral lung compared to 3D-CRT.
• PT and IMPT achieved near-zero maximum doses to the heart and esophagus, significantly lower than 3D-CRT.
• IMPT showed a greater reduction in irradiated lung volume (V2Gy) compared to PT and 3D-CRT.
• Deep inspiration breath hold (DIBH) improved DVHs for the ipsilateral lung across all treatment modalities.

Conclusions:

• Proton therapy offers modest dosimetric advantages for SBRT of lung lesions compared to photon therapy.
• The clinical significance of these dosimetric benefits regarding side effects and local control requires further investigation in clinical trials.