Ovarian cancer is the eighth most common cancer in women in Korea, with 2,600 cases occurring annually, and the number of cases is steadily increasing. There is no practical method for early detection of ovarian cancer, and 75 percent of patients are diagnosed with advanced stage. The treatment of ovarian cancer is based on surgical removal and platinum-based chemotherapy. The cell-free DNA (cfDNA) test has the advantage of being able to track and monitor mutations of tumor origin noninvasive.

The objective of this study was to assess the feasibility of circulating tumor DNA (ctDNA) as a biomarker for cancer recurrence in ovarian cancer after surgery. Diagnosis and prognosis evaluation using conventional methods such as CA-125, radiologic examination (CT), had limitations in diagnosing and prognostic observation of ovarian cancer. For precise diagnostic purposes, CA-125 had limitations because it was detected as positive value when the tumor size is enough large or states of metastasis, and CT-based diagnosis is practicable only when the size of tumor is detectable.

However, cell-free DNA can be detected even if the tumor size is small because it detects very small amount of mutation gene in the blood. In addition, the detection of tumor cell DNA from circulating blood can be a clinical decision making point whether to continue or stop chemotherapy.

In this study, the investigators collect whole blood from patients with ovarian cancer undergoing surgery. Control samples will be obtained from patients undergoing surgery for benign adnexal disease with CA125 >35U/ml. In ovarian cancer patients, blood samples will be collected prospectively every 3 months after surgery. Mutations found at the initial sample will be monitored during chemotherapy to investigate the ctDNA pattern. The primary outcome will be progression free survival (PFS).

Inclusion Criteria:

1. Female, over 19 years of age;
2. Patients with epithelial ovarian cancer
3. Patients with Serum CA-125 >35 U/mL

Exclusion Criteria:

1. Patients in pregnancy
2. Patients being treated for cancer of other organs, including gynecological cancer.
3. Patients who has difficulty reading and understanding Korean.
4. The tester's determination that the patient will not be able to comply with the clinical trial procedures.
5. Patients with severe infections or other serious medical problems that have resulted in impairment of the patient's function, making it difficult to the trial.

Patients, with epithelial ovarian cancer and patients with benign adnexal disease with serum CA-125 >35 U/mL