Usefulness of monitoring serum carcinoembryonic antigen (CEA) to define response to chemotherapy and its correlation with survival in patients with non-small cell lung cancer with abnormal baseline CEA levels.

Abstract

e18044 Background: Carcinoembryonic antigen (CEA, CEACAM5) is an oncofetal protein that functions as a cell-adhesion molecule. It is usually over-expressed in a variety of neoplasms; moreover, high serum CEA levels are an independent prognostic factor for recurrence and survival in patients with non small-cell lung cancer (NSCLC). To date, there are no markers that satisfactorily predict objective response to chemotherapy in NSCLC. Methods: The aim of the study was to evaluate the relationship of a change in serum CEA levels at baseline and after two cycles of treatment, to compare them with objective response (measured by RECIST) and to correlate it with progression free-survival (PFS) and overall survival (OS). Results: 182 (67.4%) of 270 patients had a baseline CEA serum level > 5 ng/mL (range 5-7,440). Treatment was platinum-based chemotherapy in 169 (92.9%) patients and a tyrosine kinase inhibitor was used in 13 (7.1%). The mean follow-up time was 12.6 mo. After two cycles of treatment, objective global response was 29.7% and ≤ 25% CEA reduction was found in 32.4%. One hundred percent of patients with complete response had a ≤ 25% CEA reduction value, 60% for partial response, 24.7% for stable disease and 9.3% for progressive disease (Pearson's X2 value 38.49, p < 0.0001). Sensitivity, specificity, positive predictive value and negative predictive value were 80%, 62%, 57% and 83% respectively. PFS was longer in patients with a 25% reduction in CEA (11.3 mo [CI 95% 9.5-13.1] vs 8.7 mo [CI 95% 7.5-9.8], p = 0.04) and OS showed a tendency for longer survival (19.9 mo [CI 95%12.3-27.5] vs 14.7 mo [CI 95% 13.2-16.1] p = 0.09). Conclusions: A 25% reduction from baseline CEA is associated with objective response and PFS. CEA is an accurate and specific predictor of objective response to treatment in locally advanced and advanced NSCLC. No significant financial relationships to disclose.