Changes in the tumor immune microenvironment during disease progression in clear cell ovarian cancer.

Objective: The tumor immune microenvironment in ovarian clear cell carcinoma has not been clearly defined. We analyzed the immunological changes from treatment-naive to recurrence to correlate them with clinical outcomes.

Method: We compared the changes in immune infiltration of advanced-stage ovarian clear cell carcinoma samples before treatment and at the time of recurrence via immunohistochemistry (Programmed Cell Death-ligand 1 (PD-L1), cluster of differentiation 8 (CD8+), forkhead box P3 (Foxp3+)), tumor-infiltrating lymphocytes (TIL), and next-generation sequencing (54 patients). We analyzed the association between platinum sensitivity status and tumor immune microenvironment.

Results: Immunohistochemistry revealed significantly increased PD-L1 (p=0.048) and CD8+T cells (p=0.022) expression levels after recurrence. No significant differences were observed in TIL density or Foxp3+T cells. There was no significant correlation between TIL, PD-L1, CD8+T cell, and Foxp3+T cell levels in treatment-naive tumors and survival outcomes. The most common genomic alterations were PIK3CA (41.7%) and ARID1A (41.7%) mutations. There were no differences in the immunological changes or survival outcomes according to PIK3CA and ARID1A mutations. Patients with recurrent platinum-sensitive disease showed higher TIL expression levels. There were no significant differences in PD-L1, CD8+T cells, or Foxp3+T cells between platinum-sensitive and platinum-resistant diseases.

Conclusion: We characterized the tumor immune microenvironment in patients with advanced-stage ovarian clear cell carcinoma. PD-L1 and CD8+T cell expression significantly increased after recurrence. Whether this could be used to select patients for immunotherapy in the recurrence setting should be investigated.