Towards biologically driven adaptive radiotherapy in head and neck cancer: Head and neck adaptive radiotherapy

Adaptive radiotherapy (ART) refers to radiotherapy in which the dose distributions are adapted during the course of radiation. This is done to compensate for anatomical changes that may occur, such as shrinkage of the tumour and weight loss, which may result in higher dose to organs at risk, such as the oral cavity and salivary glands.
For the development of ART that can be used in daily practice, two major issues were addressed: 1) How to early identify patients that may benefit from ART, and 2) when are the dose distribution changes such that radiation plan adaptation is required to prevent an increase in dose that would result in more complications.
To this purpose, we successfully developed methods to recalculate the dose at different time points during the course of radiation to enable recalculation of the risk of complications using prediction models. We found that the changes in the dose to organs-at-risk in the first two weeks could be used to correctly identify patients for ART to prevent higher risks of complications. At the same time, unnecessary ART could be prevented in 88% of the patients, which makes this procedure highly cost-effective.
We further investigated the variations of dose to organs-at-risk in different re-planning scenarios. Results showed that two re-planning sessions were sufficient to limit the increase of dose to most OARs to prevent that patients would develop more complications for the rest of their lives.