Immune PET and Proteomics for the Assessment of Response to Spatially Fractionated or Palliative Radiotherapy With or Without Immunotherapy

The aim of the study is to evaluate the response to four schemes of treatment with novel diagnostic tools - Immuno-PET and proteomics as well as standard imaging (magnetic resonsonce imaging and computed tomography). Two fractionation schedules of radiotherapy will be used. The first will be a common standard of palliative irradiation - 20 Gy delivered in five fractions of 4 Gy (SHORT). The other is called Spatially Fractionated Radiotherapy (SFRT). SFRT is delivered in one fraction of 20 Gy but the dose is diversified inside the tumor to produce areas of high and low doses distributed alternately. This kind of irradiation may be able to stimulate immune response and improve the efficiency of immunotherapy. A drug belonging to the class of immunotherapeutic agents - Pembrolizumab will be added to the treatment scheme in two arms of the study to check that assumption. The response of the target tumor will be evaluated with PET study using Pembrolizumab labeled with zirconium-89 which will show the spatial distribution of immune receptors within the target tumor and other involved sites if there are any. The examination will be repeated after the treatment to evaluate changes in distribution of the immune receptors necessary for the drug to work. Additionally, the researchers will repeatedly test the presence and concentration of a wide panel of proteins in blood to evaluate response to the treatment more precisely.