Durable Response to Chemoimmunotherapy in a Patient with RefractoryMetastatic Ovarian Clear Cell Carcinoma: A Case Report and Literature Review.

OBJECTIVE: Ovarian clear cell carcinoma (OCCC) frequently exhibits resistance to conventional chemotherapy with limited treatment options. This study reports a heavily pretreated advanced case with liver metastases to investigate the efficacy of gemcitabine combined with PD-1 inhibitor in such refractory patients. METHODS: We present a case of stage IIIC OCCC that progressed after first-line platinum-based chemotherapy. The patient was treated with gemcitabine incombination with the PD-1 inhibitor toripalimab. Genetic alterations were analyzed using next-generation sequencing, and PD-L1 expression was assessed by immunohistochemistry (Combined Positive Score, CPS). Treatment response andsafety profiles were regularly monitored. RESULTS: The combination therapy induced a complete remission lasting over 24 months, with a manageable safety profile. Molecular profiling revealed a loss-of-function mutation in ARID1A, which may enhance tumor sensitivity to gemcitabine, while elevated PD-L1 expression (CPS = 30) may serve as a predictive biomarker for immunotherapy response in OCCC. Notably, the deep and durable clinical response observed suggests a potential synergistic effect between gemcitabine and immunotherapy, wherein ARID1A deficiency-induced chemosensitivity may prime the tumor microenvironment for enhanced immune checkpoint inhibition, offering a compelling rationale for this combination strategy in platinum-resistant OCCC. CONCLUSION: This study proposes a promising therapeutic strategy for advanced OCCC and supports the clinical value of molecular profiling-guided treatment. Both ARID1A status and PD-L1 expression warrant further validation as potential biomarkers inprospective clinical trials.