The goal of this clinical pilot trial is to learn if dose to the tumor in the lung can be safely increased using proton therapy in stage III non-small-cell lung cancer patients receiving combined chemotherapy and radiotherapy. The main questions it aims to answer are:
* Is the risk of severe radiotherapy toxicities (requiring hospital admission) within acceptable margins ?
* What is a rough estimate of the effect of the treatment under study?
Compared to standard care in our clinic, all participants in this pilot trial will
* Receive a higher dose of proton therapy to the tumor in the lung albeit with the same number of radiotherapy visits as the current standard treatment.
* Receive two additional follow-up visits at the clinic after treatment, namely 4 and 6 weeks after finishing radiotherapy.
* Two additional blood withdrawals at the last week of radiotherapy and 4 weeks after finishing radiotherapy, to measure a type of white blood cells.
* Receive an extra quality of life questionnaire at the last week of radiotherapy.