Biological optimization for hybrid proton-photon radiotherapy

Area of Science:

• Radiation oncology
• Medical physics
• Cancer treatment

Background:

• Hybrid proton-photon radiotherapy (RT) aims to expand access to proton therapy.
• Concerns exist regarding underestimation of proton biological dose effects on organs-at-risk (OARs).
• Existing methods may not fully optimize plan quality for target coverage and OAR sparing under uncertainties.

Purpose of the Study:

• Develop a hybrid RT planning method with biological dose optimization.
• Ensure clinical implementability on existing proton and photon machines.
• Achieve uniform target dose per fraction for both modalities.

Main Methods:

• Optimized proton and photon plan variables and fraction numbers.
• Minimized biological dose to OARs and surrounding tissues.
• Used a probabilistic formulation for robust optimization against setup and range uncertainties.
• Employed an iterative convex relaxation method to solve nonconvex optimization problems.

Main Results:

• Hybrid planning with biological dose optimization eliminated biological dose hot spots in normal tissues.
• Achieved superior overall plan quality and OAR sparing compared to proton-only or photon-only plans.
• Demonstrated effective mitigation of biological dose underestimation.

Conclusions:

• Presents a novel hybrid biological treatment planning method.
• Offers reduced biological hot spots and superior plan quality.
• Ensures clinical deliverability and robustness on existing RT machines.