This prospective observational study is to assess the dynamics of circulating tumor DNA (ctDNA) in patients with advanced epithelial ovarian cancer (EOC) undergoing surgery, adjuvant chemotherapy, followed by poly adenosine diphosphate-ribose polymerase (PARP) inhibitors until disease progression or the end of the study. All patients will be closely monitored throughout the course of disease by a tumor-informed bespoke ctDNA assay as well as traditional methods of surveillance, such as CA125 and imaging. This study may provide preliminary evidence for ctDNA-guided treatment decisions in future clinical practice.