Improving workflow for adaptive proton therapy with predictive anatomical modelling: A proof of concept

•We propose a strategy to use our previously proposed predictive models in head and neck patients in offline adaptive proton therapy.•The model provides a prediction of the patient’s anatomical progression throughout the course of treatment.•The predicted anatomy provides the opportunity to create adaptive radiotherapy plans in advance, increasing workflow efficiency.•The adaptive plans based on the predicted anatomy provide clinically acceptable plans with good target coverage, comparable to a standard offline adaption.•The predicted plans can be applied as soon as plan adaption is triggered by the clinical criteria. This can help to reduce the mean dose to the parotid glands as compared to a standard offline adaptive strategy.