Expression of PD-L1 in non-small cell lung cancer: a series of 1,107 cases
Session type: Poster / e-Poster / Silent Theatre session
Theme: Diagnosis and therapy
PD1 therapy is now available for patients with various types of tumours; trials have shown that PD-L1 expression in tumour cells is a reliable predictive marker of pembrolizumab response in non-small cell lung cancer (NSCLC); the threshold for positivity varies between cancers and assays.
Pembrolizumab is available for first- and second-line treatment for patients with advanced NSCLC, whose tumours express PD-L1. The cut offs are 1% for second-line treatment and 50% for first-line treatment, when using the Dako PD-L1 IHC 22C3 pharmDx test.
We have been testing NSCLC (first- and second-line) since April 2016. Here, we present our rates of PD-L1 expression and relate these to patient demographics, histology, and rates of EGFR and ALK alteration.
The results of tumours tested using the Dako PD-L1 IHC 22C3 pharmDx test were retrieved from our database (1,107 results). PD-L1 expression was estimated quantitatively and graded as being negative (<1%), weakly positive (1-50%) or strongly positive (>50%). This was correlated with patient age and sex, tumour histology and the presence of EGFR and ALK alterations.
54% of tumours were negative, 20% weakly positive and 26% strongly positive for PD-L1 expression. There was no significant association between PD-L1 expression and patient sex or age. PD-L1 expression was similar in adenocarcinoma (46%) and squamous cell carcinoma (42%). There was an inverse relationship between PD-L1 expression and rates of EGFR mutation. No tumours tested were ALK-positive.
We report on a large series of NSCLC tested for PD-L1 expression in a molecular pathology diagnostic service; we show that the PD-L1 expression rate is similar to that reported in the KEYTRUDA KEYNOTE-001 trial. Our results show that testing is feasible in routine practice with a relatively low level of failure; that any type of NSCLC can express PD-L1; and that PD-L1 and EGFR mutations are not mutually exclusive.