P2.03b-094 Prognostic Value of Serum Carcinoembryonic Antigen during Conventional Chemotherapy in Advanced (Non-)Small Cell Lung Cancer: Topic: Biomarkers

Abstract

Carcinoembryonic antigen (CEA) is used as a biomarker in colon carcinoma, however in patients with (non-)small cell lung cancer ((N)SCLC) increased serum CEA levels are commonly found. Since decline of high CEA levels in colon carcinoma is predictive for objective response, it is hypothesized that (N)SCLC is also associated with increased CEA concentrations and decreases in CEA levels have prognostic value for therapy response. In this retrospective observational study, changes in CEA levels during first-line conventional chemotherapy were studied in 194 patients with advanced (N)SCLC. CEA data prior to treatment (baseline), on week 3, 6 and 12 were correlated with radiologic objective response, defined as partial or complete response according to RECIST 1.1, overall survival (OS) and presence or occurrence of brain metastases. In total, 122 patients (62.9%) receiving standard chemotherapy between 2012-2016 had elevated baseline CEA levels (>5 ng/mL) with overall radiologic response on week 12 of 27.0% (objective response patients without elevated baseline CEA 15.3%). Within these patients, statistically significant correlations were observed between CEA response (20% decline over baseline level) on week 6 and radiologic objective response on week 12 (OR=4.3, CI=1.8-11.1, p<0.001), resulting in a positive and negative predictive value of CEA levels of 65.9% and 69.5% respectively. When adjusted for tumor histology, significant differences in objective response were found in week 12 (NSCLC 15.2% vs SCLC 41.0%, p=0.001) and in patients with elevated baseline CEA (NSCLC 21.7% vs SCLC 43.3%, p=0.032). Statistically significant associations were found between CEA responses on week 6 and objective response on week 6 (OR=4.3, CI=1.8-11.1, p<0.001, adjusted OR=3.9) and CEA responses on week 3 and objective response on week 6 (OR=3.3, CI=1.3-8.5, p=0.007, adjusted OR=2.6). Median survival was 567 days, without significant differences according to CEA levels at diagnosis. No statistically significant associations were found between CEA responses on week 3, 6 and 12 and OS. High CEA concentrations at baseline were not associated with brain metastases at diagnosis or diagnosed within 3 months, even when adjusted for tumor histology. This is one of the first studies in advanced lung cancer which describes that CEA levels appear to be closely associated with objective response. These results show that CEA could be a predictive marker for chemotherapy efficacy in patients with advanced (N)SCLC. Further research to reveal whether CEA decline also predicts response in (N)SCLC patients undergoing novel targeted therapies or immunotherapy is ongoing.