Prognostic Significance of PD-L1 Expression by Tumor-Associated Immune Cells in Serous Ovarian Carcinoma

BACKGROUND: Current research is focused on the prognostic significance of tumor-infiltrating lymphocytes and activation of antitumor immune responses in ovarian carcinoma treatment. AIM: The work aimed to analyze the relationships among overall survival, progression-free survival, clinical factors, and the expression of PD-L1, CD3, CD4, CD8, CD14, and CD16 receptors in tumors from patients with serous ovarian carcinoma. MATERIAL AND METHODS: A prospective study was conducted to assess the expression of tumor-associated immune cells (i.e., CD3, CD4, CD8, CD14, and CD16) and PD-L1 receptor using immunohistochemistry in the tumor microenvironment of 120 patients with serous ovarian carcinoma treated at the Primorsky Regional Oncology Dispensary between 2019 and 2021. Based on the histological type of epithelial ovarian carcinoma, high-grade serous carcinoma was identified in 81.7% patients and low-grade serous carcinoma in 18.3%. Primary cytoreductive surgery was conducted in 70.0% cases. Complete or optimal cytoreduction was achieved in 57.5% primary and interval surgeries. The patients received combination therapy, with platinum- and taxane-based regimens used as first-line chemotherapy. BRCA1/2 gene mutations were identified in 28.3% patients with ovarian carcinoma. Additionally, PD-L1 expression was positive in 39.2% patients, notably in 14 patients with high-grade serous carcinoma. None of the patients with PD-L1 expression 1% had BRCA1/2 mutations. Primary treatment, involving surgical intervention combined with cycles of antitumor chemotherapy, was administered at the Primorsky Regional Oncology Dispensary between 2019 and 2021. Statistical analyses included comparison of overall and progression-free survival using the Kaplan–Meier method. Survival comparisons were performed using the log-rank test. Cox regression analysis was used to evaluate hazard ratios of various clinical and pathologic factors. RESULTS: Overall survival in patients with serous ovarian carcinoma was significantly influenced by: 1) disease stage, 2) tumor grade, and 3) timing, and extent of cytoreduction. Positive PD-L1 expression was observed in 14.3% patients with high-grade serous carcinoma and was associated with better progression-free survival (p = 0.007). CONCLUSION: Death and disease progression risks in serous ovarian carcinoma decrease in the absence of PD-L1 expression. Higher survival rates were associated with the expression of CD3, CD4, and CD8 in the tumor.