Hyperfractionated intensity-modulated proton therapy for pharyngeal cancer with variable relative biological...

Area of Science:

• Radiation Oncology
• Medical Physics
• Cancer Treatment

Background:

• Relative biological effectiveness (RBE) in proton therapy is influenced by biological factors and dose fractionation.
• Hyperfractionated photon therapy is effective for head and neck cancers, but its impact with variable RBE in intensity-modulated proton therapy (IMPT) requires further study.

Purpose of the Study:

• To investigate the impact of variable RBE on hyperfractionated IMPT for pharyngeal cancer.
• To determine an optimal hyperfractionated schedule using the biologically effective dose (BED).

Main Methods:

• Calculated the difference in BED (ΔBED) between variable and constant RBE schedules for clinical target volume (CTV) and soft tissues.
• Evaluated various treatment parameters (days, fractions, dose) to define ΔBED.
• Utilized BED volume histograms to compare RBE and fractionation effects.

Main Results:

• Variable RBE reduced mean BED for CTV and acute reactions but increased it for late reactions in conventional schedules.
• A hyperfractionated schedule of 80.52 Gy/66 fractions over 6.5 weeks was identified.
• This schedule increased mean BED for CTV and acute reactions but decreased it for late reactions compared to conventional IMPT.

Conclusions:

• Variable RBE has a potential effect on IMPT for pharyngeal cancer, but hyperfractionation may mitigate or enhance this.
• The proposed hyperfractionated schedule shows promise for IMPT in pharyngeal cancer, warranting conservative clinical application due to biological uncertainties.