Ovarian cancer ranks third in the incidence of gynecologic malignancies, while mortality ranks first. The tumor marker CA125 is the most concerned tumor marker in the clinical monitoring prognosis of ovarian cancer, and an elevated CA125 indicates a later stage and a worse prognosis. However about 20% of patients with ovarian cancer have low CA125 expression. Therefore, CA125 is not sensitive to some ovarian cancers with a high risk of recurrence. How to improve the diagnostic performance of these CA125-insensitive patients is a difficult problem in current research. Minimal residual disease (MRD) refers to the residual tumor components in the body of tumor patients after achieving complete remission through treatment. MRD detection is mainly achieved by liquid biopsy, and residual tumor components can be detected by circulating tumor DNA (ctDNA). This study aims to explore the value of MRD (ctDNA) in the risk assessment of CA125 non sensitive ovarian cancer populations by combining ctDNA with traditional imaging and serological tumor markers.

Inclusion Criteria:

• Age 18-75;
• Pathologically confirmed ovarian cancer;
• CA125 ≤200U/ml at first diagnosis or recurrence;
• Physical condition score PS ≤ 2 points;
• Enough tumor samples for WES detection;
• Patients and their families can understand and are willing to participate in this study and provide written informed consent.

Exclusion Criteria:

• Patients unable to provide sufficient tissue / blood samples for research detection;
• Pregnant or lactating women;
• Other diseases considered by the research doctor to affect the prognosis and survival;

This study intends to include 35 patients with low CA125 level ovarian cancer at first diagnosis or recurrence between the ages of 18-75 years old.