Abstract 206P
Background
Atezolizumab has been approved for use in advanced recurrent triple negative breast cancer (TNBC) whose tumours test positive for programmed death-ligand 1 (PD-L1). However, controversy remains regarding when to test for PD-L1. We retrospectively studied the PD-L1 positive rates in biopsy, surgical, and recurrent specimens for TNBC treated with neoadjuvant chemotherapy (NAC). We also looked at alterations in PD-L1 and what the significance of these alterations.
Methods
28 TNBC biopsy samples taken before NAC, 16 surgical specimens with residual tumour after NAC, and 5 specimens from recurrences were obtained. We performed PD-L1 immunohistochemistry on tumour cells (TC) and on tumour infiltrating immune cells (IC) using the SP142 antibody. PD-L1 score was determined according to the manufacturer’s instructions.
Results
The PD-L1 positive rates of the biopsy samples before NAC were IC0: 46.4%, IC1: 25.0%, IC2: 21.4%, IC3: 7.1%, TC0: 28.6%, TC1: 28.6%, TC2: 42.9%, TC: 0%. In the surgical specimens after NAC, PD-L1 showed almost no change in IC (P = 0.38), but the score significantly decreased in TC (P < 0.001). Prognosis in the PD-L1 strong positive group (IC ≥ 2 and TC ≥ 2) was worse than the other groups for both disease free survival (DFS) and overall survival (OS) (P = 0.004 and P = 0.041, respectively). Among the cases in which the tumour remained after chemotherapy, increased PD-L1 in IC suggested a good prognosis for both DFS and OS (P = 0.067, P = 0.041, respectively).
Conclusions
This is the first study to research PD-L1 expression before and after chemotherapy in breast cancer, and indicates that it might be feasible to identify a group of TNBC patients with a better prognosis with non-pathological complete response following NAC.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
The authors.
Funding
Has not received any funding.
Disclosure
All authors have declared no conflicts of interest.