The predictive role of PD-L1 expression and CD8+ TIL levels in determining the neoadjuvant chemotherapy response in advanced ovarian cancer.

Objective: To analyze how the PD-L1 expression and CD8+ tumor infiltrating lymphocyte (TIL) levels in biopsy samples before neoadjuvant chemotherapy (NAC) can predict chemotherapy response score and survival for advanced high-grade serous ovarian cancer. Methods: We retrospectively analyzed 45 patients with advanced epithelial ovarian cancer between 2010 and 2018, who had received at least three cycles of neoadjuvant chemotherapy. PD-L1 expression and CD8+ TIL levels were evaluated by immunohistochemical staining in the pre-NAC tumor samples from which the patients had been diagnosed. The post-NACT tissue samples taken during interval debulking surgery (IDS) were used to evaluate the chemotherapy response score (CRS). Results: Among all the patients, CRS 1 (no response) was found in 8 patients, CRS 2 (partial response) in 28 patients, and CRS 3 (complete response) in 9 patients. A total of 20 (44.4%) patients had high intraepithelial CD8+ TIL levels, and 35(77.8%) patients had high expression stromal CD8 TIL. No statistically significant relationship was found between high and low expression of intratumoral/stromal CD8+ TIL levels with PFS and CRS. The study found that 33(73.3%) patients had high levels of stromal PD-L1 expression and 28(62.2%) patients had high levels of intratumoral PD-L1 expression. In the intratumoral PD-L1 group, patients with low expression had a PFS of 28 months, whereas those with high expression had a PFS of 17 months (p=0.028). Among the patients with high intratumoral PD-L1 expression, 23 (82.1%) patients showed CRS2, 4 (44.4%) showed CRS3, and only 1(3.6%) showed CRS1 (p=0.000). However, high or low expression stromal PD-L1 did not significantly affect PFS and CRS (p=0.928 and p=0.305; respectively). Conclusions: We found that intraepithelial PD-L1 expression levels in diagnostic biopsy in ovarian cancer can predict the chemotherapy response score in interval debulking surgery.