PhD defence N. (Noortje) Verschoor

Below is a brief summary of the dissertation: 

In the past century, cancer research has led to improved diagnoses and treatments, significantly enhancing patient survival and quality of life. However, some patients still experience metastasis, for which a cure is often not possible. Improving treatments for this group remains an important research goal.

Part 1 of this dissertation focuses on characterizing tumor material. Research shows that liquid biopsies, such as circulating tumor cells (CTCs) and circulating tumor DNA (ctDNA), offer less invasive alternatives to traditional tissue biopsies. Chapters 2-4 emphasize that although liquid biopsies have potential, the methods and interpretations are not yet standardized. Clinical studies, for instance, indicate that determining HER2 positivity via CTCs remains challenging and has not yet significantly improved treatment outcomes.

Part 2 of the dissertation examines the clinical value of the circulating tumor load (the amount of CTCs or ctDNA) as a prognostic biomarker in both metastatic and non-metastatic disease. The mFast-SeqS method demonstrates that aneuploidy in ctDNA has reliable prognostic value. The potential of ctDNA and CTC detection in determining the need for adjuvant therapy in non-metastatic cancer is also explored. While these methods are promising, further validation is needed.

Conclusion: Liquid biopsies can improve treatment decisions for individual patients by enabling targeted therapies. The research in this dissertation contributes to understanding the validity and applicability of these techniques, but further study is needed to effectively integrate them into clinical practice.