Pattern of tumor-infiltrating lymphocytes (TILs) and PD-L1 expression in primary and metastatic epithelial ovarian cancer (EOC).

Abstract

64 Background: Tumour immune response plays a critical role in progression and prognosis of EOC, however patterns of TILs and PD-L1 expression in primary and metastatic disease remain poorly described. Methods: Patients treated with neoadjuvant chemotherapy (NACT) for advanced EOC, between 2002-2014, and available sequential tumours (pre-NACT, post-NACT, or relapse) were retrospectively identified. Stromal TILs (sTILs) were evaluated according to the International TILs Working Group 2014 (Salgado 2015) on whole sections, and scored as a percentage of stromal area. Immune cell PD-L1 expression was evaluated by immunohistochemistry (E1L3N clone, Cell Signaling) in a smaller number of tumours. Cutoffs for analysis were: high sTILs ≥50%, PD-L1 positivity ≥5% membranous staining. Results: Among a total of 236 tumour samples from 150 patients (110 pre-NACT, 111 post-NACT, and 15 relapse tumours) median sTILs levels was significantly higher in metastatic tumours ( n=151) compared with primary tumours ( n=85) (median 30, IQR 10-50 vs. 15, IQR 5-30, p=0.0004). Among diagnostic samples, median sTILs level was 20 (IQR 10-45, n=85) in metastatic tumours compared with 10 (IQR 5-20, n =25) in primary tumours ( p=0064). Similarly in post-NACT samples, median sTILs level was 40 (IQR 15-60, n=51) in metastatic tumours compared with 20 (IQR 6.25-30, n=60) in primary tumours ( p=0026). Among relapse samples median sTILs level was 30 (IQR 10-50, n=15). Among all available samples ( n=97) PD-L1 positivity was detected in 33% (9/30) of primary and 50% (34/68) of metastatic tumours (Fisher’s exact test OR 2.3, 95%CI 0.94-5.4, p =0.08). Conclusions: In patients with EOC there is increased lymphocytic infiltration in both synchronous metastatic disease at diagnosis, and metachronous metastatic disease at relapse, compared with the primary tumour. This suggests increased immunogenicity as disease progresses. Furthermore, there is a trend towards upregulation of the PD-L1 immune checkpoint with disease progression.