Abstract 1003P
Background
The determination of predictive biomarkers for immune checkpoint inhibitors (ICIs) is one of the current challenges in oncology. At present, we are unaware of the existence of response patterns to ICIs. Different studies of non-small cell lung cancer (NSCLC) have shown how mutations in the TP53 gene correlate with different responses to ICIs. Strong and diffuse immunoexpressions of p53 by immunohistochemistry (IHC) are generally interpreted as a likely indicator of a TP53 gene mutation. The objective of this study is to assess the expression of p53 protein via ICH in NSCLS as a predictive biomarker of response to ICIs.
Methods
Retrospective hospital-based study of patients with NSCLC who were treated with Nivolumab in the Department of Oncology of the University Hospital of Salamanca. All diagnostic biopsies were studied via IHC by measuring the expression of the p53 protein. A survival correlation (Kaplan-Meier, Log Rank test, SPSSv25) was performed by subgroups of p53 expression in months (m). Statistical significance was established a priori at p<0.05.
Results
In all, 73 biopsies were studied (36 adenocarcinoma, 34 squamous, 3 undifferentiated). In 47 (64,4%) biopsies, the cellular expression of p53 was <10% (Group A or A), and in 26 (35,6%) it was ≥10% (group B or B). No differences were observed in progression-free survival (PFS) (A 4m vs B 7m; p=0.181) or overall survival (OS) (A 12m vs B 20m; p = 0.149). Statistically significant differences were observed in PFS when the groups in PDL1≥10% were compared (A 5m vs B not reached median; p=0.047), and in OS (A 9m vs B not reached median; p=0.02). No differences were observed in PFS (A 4m vs B 4m; p=0.925) or OS (A 13m vs B 9m; p=0.972) in PDL1<10%.
Conclusions
Despite the limited nature of our sample, a trend towards a greater response to ICIs was observed in PFS and OS in patients with a high expression of p53 protein (TP53 gene mutation) and PDL1≥10%. Mutations in TP53 appear to show a correlation with the response to ICIs in tumours with high expression of PDL1. New studies are needed in the future to assess the expression of p53 via ICH as a new predictive marker of response to ICIs in NSCLC and other solid tumours.
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.