Using gEUD based plan analysis method to evaluate proton vs. photon plans for lung cancer radiation therapy

Area of Science:

• Radiation Oncology
• Medical Physics

Background:

• Current clinical guidelines for lung cancer radiation therapy are based on photon (IMRT) experience.
• Proton therapy offers potential advantages but requires specific evaluation methods.

Purpose of the Study:

• To evaluate the efficacy of DVH-based clinical guidelines, derived from photon therapy, when applied to proton therapy for lung cancer.
• To develop and apply a radio-biological model for a more accurate comparison of proton and IMRT plans.

Main Methods:

• Generated and compared intensity-modulated radiation therapy (IMRT) and proton therapy plans for 10 lung cancer patients.
• Developed a generalized equivalent uniform dose (gEUD) based evaluation method using literature-reported model parameters.
• Introduced a deficiency index (DI) to quantify potential plan inferiority.

Main Results:

• Proton plans showed lower normal lung V5Gy but similar V20Gy and target coverage compared to IMRT.
• While current guidelines favored proton plans, gEUD analysis revealed potential inferiority in 8 out of 10 patients.
• DI and curve crossing analysis identified 4-6 patients for whom IMRT might be superior for lung sparing.

Conclusions:

• Directly applying photon-derived guidelines to proton therapy for lung cancer may be unreliable.
• A comprehensive radio-biological evaluation is crucial to determine actual patient benefit from proton therapy.
• New evaluation strategies are needed to optimize lung cancer treatment planning with protons.