A Comparative Study of the Treatment of Real-world Patients With Clear Cell Carcinoma of the Ovary

The goal of this observational study is to learn about the treatment effectiveness of physician's choice of chemotherapy and the immune checkpoint inhibitor (ICI)-based therapy in patients with relapsed/refractory ovarian clear cell carcinoma (OCCC), and compare the treatment response with the phase II, single-arm clinical trial INOVA to investigate the efficacy of combinational therapy of sintilimab plus bevacizumab. The main questions it aims to answer are: * What is the efficacy of physician's choice of chemotherapy in relapsed/refractory OCCC patients in the real world? * Is ICI-based therapy more effective than physician's choice of chemotherapy in real-world for relapsed/refractory OCCC patients? * Dose the combinational regimens of sintilimab plus bevacizumab in Sintilimab Plus Bevacizumab in Recurrent/Persistent Ovarian Clear Cell Carcinoma (INOVA) trial more effective than physician's choice of chemotherapy? Participants will be respectively retrieved and extracted de-identified, longitudinal electronic health records (EHR)-derived data.