Treatment Planning Adaptations for Hypoxia in Proton Therapy for Head and Neck Cancer

Abstract

Aim: Perform treatment planning adaptations for proton therapy to correct for hypoxia in head and neck cancer (HNC). Material and methods: Hypoxic subvolumes were defined using three pO2 (oxygen partial pressure) thresholds, 5 mmHg, 7.5 mmHg and 10 mmHg, using [18F]EF5 PET/CT images for a HNC patient. FLUKA Monte Carlo simulations were then performed to calculate the oxygen enhancement ratio (OER) and relative biological effectiveness (RBE) weighted dose. Three additional treatment plans were made, one for each pO2 threshold, before OER adapting the dose objectives for the hypoxic subvolumes using Eclipse treatment planning system. Results: the method successfully defined and increased the biological dose for three pO2 threshold defined hypoxic regions. However, the dose to the surrounding normoxic tumour tissue was also increased.