366 Prognostic impact of PD-L1 expression in epithelial ovarian cancer: a cohort of 49 patients

Introduction/Background* Role of checkpoint inhibitors in ovarian cancer is still unknown and results from ongoing clinical trials are still awaited. We aim in this study to assess the expression of PD-L1 using the Combined Positive Score (CPS) and to evaluate its impact on the overall survival in a cohort of 49 patients diagnosed with high-grade serous ovarian cancer. Methodology Medical charts were reviewed of 49 patients with high-grade serous ovarian cancer operated on at the gynecologic oncology department in Hotel-Dieu de France hospital, Lebanon, between 2015 and January 2020. Immunohistochemical staining was performed for PD-L1 (Agilent Dako, PDL-1 IHC 22C3) and for TP53 (Agilent Biogenex, clone D07, 1:100 dilution) on whole tissue sections from a representative block of formalin-fixed, paraffin-embedded tumor tissue. We looked for correlation between PD-L1 status and overall survival/recurrence. We also looked for correlation between PD-L1 status and TP-53 mutation. Result(s)* 55% of patients presented a positive PD-L1 status. No correlation was found between the PD-L1 status and the stage of the disease. Lymph node status was similar between the two cohorts, positive vs. negative CPS score (p = 0.927). Median follow-up was 36 months (range, 12 – 72 months). Survival rate was similar between the two cohorts, positive vs. negative PD-L1 status (88.9% vs. 72.7% respectively, p = 0.14). No correlation was found between recurrence rate and PD-L1 status (p = 0.184). Also, no correlation was found between PD-L1 status and TP-53 type (wild vs. mutated) (p = 0.154) Conclusion* PD-L1 status does not seem to have a prognostic impact in our series of patients with high-grade serous epithelial ovarian cancer. Also, patients with TP53 mutation do not present increased expression of PD-L1 in comparison to patients with TP53 wild-type.