Abstract 6106: The effect of neoadjuvant chemotherapy on tumor immune microenvironment in ovarian cancer

Abstract Background: Ovarian cancer (OC) is a highly lethal gynecologic malignancy, neoadjuvant chemotherapy (NACT) with interval de-bulking surgery (IDS) is an established strategy for woman with advanced epithelial ovarian cancer (EOC). Tumor infiltrating lymphocytes (TILs) play an important role in the pathogenesis of OC. However, the effect of NACT on tumor immune microenvironment (TIME) has not been evaluated. Methods: All patients underwent NACT with IDS. Formalin-fixed paraffin-embedded tissue samples were collected from biopsy specimens and the corresponding post-NACT surgical specimens. The densities and percentage of specific TILs [CD8+, CD3+, CD4+, CD20+, tumor associated macrophages (TAMs), dim CD56+NK, bright CD56+NK, PD-1+ etc.] within the TIME were analyzed by multiplex immunohistochemistry (3DMedcines Inc.). Serum CA 125 was measured 3-weekly per protocol and evaluated the response to NACT using GCIG CA125 response criteria. Results: A total of 28 patients were enrolled in this study with planned IDS after NACT. Of 25 patients evaluated by GCIG CA125 response criteria, 76% (19/25) had a CA125 response. In CA125 response patients, we observed significant recruitments of the densities and percentage of CD8+ in tumor, percentage of PD-1+ cell in tumor after-NACT vs before-NACT (34.85/mm3 vs 110.54/mm3, p=0.0258; 0.50% vs 1.73%, p=0.0132; 0.53% vs 2.66%, p=0.0576, respectively), while no significant change was found in TAMs, NK cells and CD20+ cells. However, in CA125 non-response patients, the TILs in tumor did not change significantly. Conclusion: NACT could release the tumor associated antigen by killing tumor cells for uptake by tumor-infiltrating dendritic cells and promote the infiltration of CD8+ and PD-1+ T lymphocyte in CA125 response OC patients. Given the limited clinical prognostic information and the number of patients in this study, the results of this study will need confirmation in larger studies in the future. Citation Format: Guangming Cao, Dingchao Hua, Lina Cui, Xiaochen Zhao, Shuzhen Wang, Lei Zhu. The effect of neoadjuvant chemotherapy on tumor immune microenvironment in ovarian cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 6106.