A personalized treatment strategy is not yet possible for all cancer patients. In this thesis, cancer markers in blood were studied to help select and monitor therapy to refine cancer treatment per patient. In the blood, DNA from tumor cells can be present, which is called circulating tumor DNA (ctDNA). CtDNA often contained the same genetic information as tumor tissue. Consequently, ctDNA tests could be used for genetically-matched treatment selection. Additionally, the level of ctDNA in blood has a prognostic value, with high ctDNA levels associated with a shorter survival. Finally, the changes in the level of ctDNA during treatment reflected therapy response. A reduction in ctDNA was associated with a good response to therapy and persistent or increasing ctDNA levels were associated with therapy resistance. Consequently, blood tests might help select treatments or help navigate early therapy switches to refine cancer treatment per patient.
Sofie Tolmeijer (1995) obtained her Master’s degree in Biomedical Sciences, cum laude, at the Leiden University in 2019. Afterward she started her PhD research at the department of Medical Oncology in collaboration with the department of Tumor Genetic at the Radboudumc. Currently, she is working as a postdoctoral researcher at the Vancouver Prostate Centre, University of British Columbia (Canada).