Robust Four-Field and Arc LET-Optimized Proton Prostate Cancer Treatment Plans With Urethral Sparing

Area of Science:

• Radiation Oncology
• Medical Physics
• Proton Therapy

Background:

• Proton therapy utilizes pencil beam scanning for precise dose delivery.
• Optimizing Linear Energy Transfer (LET) can enhance the biological effectiveness of proton therapy.
• Urethral sparing is crucial in prostate cancer treatment to minimize side effects.

Purpose of the Study:

• To develop LET-optimized pencil beam scanning proton therapy plans for prostate cancer.
• To achieve clinically acceptable range robustness and effective urethral sparing.
• To evaluate the trade-offs between robustness, LET, and dose distribution.

Main Methods:

• Creation of two-beam, four-beam, and arc LET-optimized treatment plans.
• Incorporation of urethral sparing by reducing physical dose to the urethra.
• Statistical comparison of LETd, RBE-doses, TODRs, and V80% between LET-optimized and reference SFO plans across 12 patients.

Main Results:

• LET-optimized plans demonstrated a trade-off between robustness and high LETd.
• Four-beam and arc plans showed statistically significant increases in CTV PSV-U D95 RBE-dose compared to SFO plans.
• High LETd in the periurethral prostate prevented underdosage, achieving urethral sparing; V80%s were decreased in four-beam and arc plans.

Conclusions:

• LET-optimized treatment plans achieve high LETd and clinical robustness for prostate cancer.
• These plans have the potential to increase the therapeutic ratio.
• Urethral sparing is implemented effectively without underdosing the periurethral prostate.