A Novel Framework for Thermoradiotherapy Treatment Planning

Area of Science:

• Oncology
• Radiation Oncology
• Medical Physics

Background:

• Thermoradiotherapy combines radiation therapy (RT) with hyperthermia (HT) to enhance tumor treatment efficacy.
• Current treatment planning optimizes RT and HT separately, with outcomes often assessed using equivalent radiation dose in 2-Gy fractions (EQD2).

Purpose of the Study:

• To introduce and validate a novel thermoradiotherapy treatment planning framework that integrates voxelwise EQD2 optimization, incorporating thermal radiosensitization and direct thermal cytotoxicity.
• To demonstrate proof-of-concept for the planning framework using simulated prostate cancer cases.

Main Methods:

• Three planning strategies were evaluated for 4 prostate cancer cases: conventional RT (60 Gy) + HT, dose-escalated RT (68 Gy) alone, and a novel approach (RT_HT + HT) optimizing EQD2 for maximum tumor control probability (TCP) considering thermal effects.
• Analyses included dose, EQD2, TCP, rectal normal tissue complication probability (NTCP), and robustness against parameter uncertainties.

Main Results:

• The novel RT_HT + HT strategy achieved the highest average TCP (94.4%), outperforming conventional RT + HT (85.9%) and RT alone (76% without HT, 92.5% with RT68).
• Rectal NTCP was comparable between RT_HT + HT (8.4%) and conventional RT + HT (8.7%), while RT68 showed higher NTCP (14.9%).
• The RT_HT + HT approach demonstrated robust TCP and NTCP across different thermal distributions and parameter uncertainties.

Conclusions:

• The proposed thermoradiotherapy planning framework effectively integrates thermal effects into EQD2 optimization, enhancing target EQD2 and TCP.
• This method achieves improved tumor control without increasing normal tissue toxicity compared to conventional approaches.
• Clinical translation requires accurate tumor- and tissue-specific data for precise hyperthermia quantification, which the framework can accommodate.