RecruitingPhase 2Diagnostic testPersonalized Timing of Interval Debulking Surgery in Advanced Ovarian CancerAbout 70% of epithelial ovarian cancer patients are diagnosed at advanced stage. When primary optimal surgery is not possible, neoadjuvant chemotherapy will followed by interval debulking surgery is one treatment option. However, there is no consensus on the optimal timing of the surgery. CA125 is a well-known tumor marker in ovarian cancer. Its kinetic change has been proven to correlate with the patients' response to chemotherapy and chance of optimal resection. This study aims to utilize the kinetic change of CA125 to customize the timing of surgery for individual patients and compare this with the standard clinical practice.