PURPOSE: In both the IMpassion 130 trial in the metastatic setting and in 
Keynote 522 in the neoadjuvant setting, patients with triple-negative breast 
cancer (TNBC) showed benefit from PD-1 axis immunotherapy. Here, we assess PD-L1 
expression on both tumor and immune cells using quantitative immunofluorescence 
to assess association with benefit from neoadjuvant durvalumab concurrent with 
chemotherapy in TNBC.
EXPERIMENTAL DESIGN: Pretreatment core needle biopsies (n = 69) were obtained 
from patients who participated in a phase I/II clinical trial (NCT02489448). The 
final analysis included 45 patients [pathologic complete response (pCR) = 18, 
non-pCR = 27] due to technical issues and insufficient tissue. Slides were 
stained using a previously validated Ultivue DNA-based Ultimapper kit (CD8, 
CD68, PD-L1, Cytokeratin/Sox10, and Hoechst counterstain). The PD-L1 expression 
was analyzed by molecular compartmentalization without segmentation using AQUA 
software (version 3.2.2.1) in three tissue compartments including tumor 
(cytokeratin-positive cells), CD68+ cells, and overall stroma.
RESULTS: In patients with pCR, PD-L1 expression was significantly higher in 
tumor cells, in CD68+ cells and in the stroma compared with patients non-pCR. 
There was no difference in the amount of CD68+ cells in the tumor or stromal 
compartments between cases with pCR and non-pCR.
CONCLUSIONS: Expression of PD-L1 in tumor cells, immune cells in stroma, and 
colocalized with CD68+ cells is associated with higher rates of pCR to 
durvalumab and chemotherapy in TNBC.