Evaluation of serum biomarker CEA and Ca-125 as immunotherapy response predictors in metastatic non-small cell lung cancer

Background/Aim: Treatment options for advanced non-small cell lung cancer (NSCLC) include immunotherapy. Elevated carcinoembryonic antigen (CEA) and cancer antigen 125 (Ca-125) levels are associated with poorer prognoses of resected NSCLC, but currently no predictive biomarkers exist for immunotherapy response. This study evaluated CEA and Ca-125 as predictive biomarkers for immunotherapy efficiency in patients with metastatic NSCLC. Patients and Methods: The single-centre observational retrospective study includes NSCLC stage III/IV patients treated with programmed death-ligand 1 (PD-L1) inhibitors nivolumab or pembrolizumab. The primary study endpoint was treatment response assessed by CT-scan following RECIST-criteria 1.1. CEA/Ca-125 serum values were determined at initiation of treatment and repeated every 2 weeks. Values closest to the day of CT-scan were compared to baseline values. Results: A total of 136 patients were treated with mono-immunotherapy. Of these, 73 patients were included in the CEA group and 53 patients were included in the Ca-125 group. Baseline CEA and Ca-125 ranged from 8.14 to 5,909 and 1.1 to 4,238 respectively. The sensitivity for Ca-125 as predictor for tumor response was 62.9% (95% CI=61.8%-63.6%), specificity 61.1% (95% CI=60.2%- 62.0%), with a positive predictive value (PPV) of 75.9% (95% CI=75.2%-76.7%). For CEA, the sensitivity was 72.0% (95% CI=71.5%-72.5%), specificity 47.1% (95% CI 46.4%- 47.8%), with a PPV of 80.0% (95% CI=79.6%-80.4%). Conclusion: Increased serum CEA might predict tumor progression in NSCLC patients treated with PD-L1 inhibitors. Unconfirmed progression accompanied by increased CEA would support discontinuation of the immunotherapy, while continuation would be advised when serum CEA is not increased.