Research Group Jan Unkelbach

With modern imaging techniques available for both diagnoses and treatment, one of the biggest uncertainties in treatment planning is the definition of the target volume, i.e. the volume to be irradiated. This especially applies to the clinical target volume (CTV), which includes regions of microscopic tumor spread that is not visible in CT, MRI, or PET images. In our group, we work on mathematical models to better quantify the locoregional progression of cancer to improve CTV definition. Our current work focuses on Head & Neck squamous cell carcinoma.

Proton therapy is often considered a radiation modality that is in principle superior to conventional radiotherapy with high energy x-rays. However, due to cost and size of the gantry, proton therapy is available only in around 100 centers worldwide, compared to more than 10’000 x-ray based radiotherapy units. We work on concepts to combine proton therapy with conventional x-rays with the goal of using limited proton resources optimally and developing cost effective proton therapy concepts with fixed beam lines.

Most radiation treatments are fractionated, i.e. the total dose is divided into fractions that are delivered over several days or weeks. In current practice, the same dose is delivered to the tumor in each fraction. We explore an idea to deliver different dose distributions each day. The different fractional dose distributions are designed such that each fraction deliveres a high dose to complementary parts of the tumor while splitting the dose more evenly in the normal tissue. Thereby, some degree of hypofractionation can be achieved in the tumor along with more uniform fractionation in normal tissues.

Modern image-guided radiotherapy systems such as the MR-Linac allow for adaptive radiotherapy, i.e. adapting the treatment to motion of the tumor and changes in the geometry from day to day. Adaptive fractionation is an approach to not only correct for motion but to exploit anatomical changes. This is achieved by increasing the dose on days when the distance of tumor and dose-limiting organ at risk is enlarged, and decreasing the dose on unfavorable days.