The Landscape of CEACAM5 Expression by Immunohistochemistry in NSCLC

Carcinoembryonic antigen-related cell adhesion molecule 5 (CEACAM5) is a target of antibody-drug conjugate therapy for NSCLC. High expression of CEACAM5 has been reported in approximately 25% of patients with lung adenocarcinoma. However, CEACAM5 expression has not been systematically examined in a real-world and large patient population with NSCLC. There are also limited data on the prognostic impact of CEACAM5 protein expression.

We assessed CEACAM5 protein expression by immunohistochemistry in two separate cohorts of patients with NSCLC to include both routine clinical biopsy and resection specimens, using the anti-CEACAM5 clone 769 antibody assay protocol and scoring scheme for the tusamitamab ravtansine clinical trials. Expression levels were categorized as high (≥50% tumor cells at ≥2+ intensity), moderate (1%-49% tumor cells at ≥2+ intensity), and negative (0/1+ intensity) and scored independently by three thoracic pathologists. Interrater reliability was determined by Kendall's coefficient of concordance and Fleiss' kappa. Association with PD-L1 and driver mutation was calculated by Fisher exact or chi-square test. Correlation with recurrence-free survival and overall survival was determined by log-rank tests.

The interrater reliability of CEACAM5 assessment was moderate among three pathologists. The overall prevalence of high CEACAM5 expression was 18%. CEACAM5 expression did not significantly correlate with tumor stage, PD-L1 expression, tumor mutation burden, and EGFR or KRAS mutations. There was no prognostic effect of CEACAM5 expression on recurrence-free survival or overall survival.

Our data revealed that 18% of routinely diagnosed clinical NSCLC samples had high CEACAM5 expression by immunohistochemistry, and its expression was not associated with oncogenic driver mutations or patient prognosis in a predominantly early stage NSCLC cohort.