Abstract 34P
Background
PD-L1 expression has shown to be predictive of response to immunotherapy in patients with metastatic triple-negative breast cancer (TNBC). It is unclear if PD-L1 expression by currently available validated assays has predictive capacity for response to chemotherapy in patients with non-metastatic TNBC.
Methods
We conducted a systematic review and meta-analysis of clinical studies to assess the PD-L1 expression as a predictor of response to chemotherapy in non-metastatic TNBC using validated assays. The primary endpoint was pathological complete response (pCR) rate to neoadjuvant chemotherapy. Secondary endpoints included the prevalence of PD-L1 expression and its impact on disease-free survival (DFS) and overall survival (OS). Moreover, RNA sequence data from the TCGA breast cancer cohort was used to define the relationship between PDCD1 and response to chemotherapy and prognosis.
Results
Nineteen studies were eligible for the meta-analysis with a total of 2319 patients with non-metastatic TNBC disease. The PD-L1-positive cohort had a significantly higher probability of achieving pCR with neoadjuvant chemotherapy (pooled OR =1.95; 95% CI: 1.39-2.73, p <0.0001). In studies which reported long-term outcomes, PD-L1 positivity was associated with better DFS and OS compared to PD-L1-negative patients (pooled HR= 0.51; 95% CI: 0.35-0.74, p< 0.0001 and pooled HR= 0.51; 95% CI: 0.27-0.94, p=0.031, respectively). RNA sequence data suggested that PD-L1 expression is a surrogate marker for the upregulation of key immune-related genes that mediate response to chemotherapy in TNBC.
Conclusions
This meta-analysis clearly shows that patients with PD-L1-negative TNBC respond less to neoadjuvant chemotherapy and are associated with poorer survival compared to patients with PD-L1-positive tumors. The newly distinct quadruple-negative breast cancer (QNBC) subtype could be considered the BC subtype with the poorest outcome.
Legal entity responsible for the study
The authors.
Funding
Has not received any funding.
Disclosure
All authors have declared no conflicts of interest.