Comparing Organs at Risk Sparing Between Intensity-Modulated Radiotherapy and Pencil-Beam Scanning Plans Based on...

Area of Science:

• Radiation Oncology
• Medical Physics
• Oncology

Background:

• Radiotherapy (RT) is a cornerstone in treating Hodgkin (HL) and aggressive Non-Hodgkin Lymphoma (aNHL).
• Photon intensity-modulated radiotherapy (IMRT) and proton therapy (PT) are key RT modalities.
• PT is a limited resource, necessitating identification of optimal use cases for patients and providers.

Purpose of the Study:

• To compare organ at risk (OAR) sparing between IMRT and pencil-beam scanning (PBS) proton therapy.
• To evaluate OAR sparing differences based on lymphoma disease location using the Ann Arbor (AA) staging system.

Main Methods:

• A cohort of 156 HL or aNHL patients treated with RT between 2007-2020 was analyzed.
• Two treatment plans (IMRT and PBS) were created for each patient at a prescribed dose of 30 Gy.
• OAR doses were assessed based on AA disease location (e.g., mediastinal involvement categorized as upper, middle, lower - UML) using absolute (AS) and relative sparing (RS).

Main Results:

• PBS demonstrated reduced mean heart dose, with the largest absolute sparing (AS) of 6.4 Gy for UML mediastinal involvement.
• Greatest AS and relative sparing (RS) for lung V20 occurred in patients with bilateral axillary involvement (20.9% AS, 53.5% RS).
• Mean breast dose sparing was greatest for patients with bilateral hilar disease (5.1 Gy AS, 58.6% RS).

Conclusions:

• Pencil-beam scanning proton therapy significantly decreases mean dose to OARs in lymphoma patients.
• The magnitude of OAR sparing with PT is influenced by the specific anatomic location of the disease.
• Anatomic location is a critical factor in determining the relative benefit of PT for lymphoma treatment.