Role of early serial change in serum carcinoembryonic antigen levels as a predictive marker for gefitinib sensitivity in Japanese patients with non-small cell lung cancer

Abstract

17029 Background: The aim was to evaluate the utility of an early change in CEA levels for predicting subsequent gefitinib sensitivity in NSCLC patients. Methods: CEA level was measured before and after the beginning of gefitinib treatment (day1) in 110 (91%) of consecutive 121 patients. Daily decline rate of CEA was simply defined for each patient as follows: (M0−Mx)/Dx/M0*100(%), with the baseline level (M0), the level on days × (Mx), and days from day 1 to day X (Dx). Results: Patient characteristics were as follows; median age: 62, M/F: 61/39%, Ad/others: 84/16% and smoker: 66%. Objective response rate and disease control rate were 28.2% and 74.5%, respectively. Median baseline CEA level was 12.6 ng/mL. Daily decline rate of CEA level from day 1 to the date on which confirmation of objective response was performed significantly differed among the response categories; median decreases in percentages were 0.86, 0.06, and −1.52%/day in CR/PR, SD, and PD patients, respectively (p < 0.0001). This association was more evident in the 70 patients with abnormal baseline CEA level (≥5.0 ng/mL). A cutoff level of −0.58% decrease per day most accurately reflected tumor shrinkage in the 70 patients, with sensitivity, specificity, and positive and negative predictive values for disease control (CR/PR/SD) of 89.1, 73.3, 92.5 and 64.7%, respectively. Among 49 (41%) patients reassessed CEA levels within the first 2 weeks since day 1, 41 could continue the treatment without any disease progression during this period. The daily decline rate in this early phase tended to differ between the responses (median; 1.57 and −0.50% in CR/PR/SD and PD, respectively; p = 0.0975), and less exactly reflected disease control with sensitivity, specificity, and positive and negative predictive values of 82.1, 40.0, 88.5, and 28.6%, respectively when a cutoff of −0.58% was applied. Conclusion: Degree of change in CEA level from the start of gefitinib treatment to confirmation of objective response significantly correlated with tumor shrinkage. As a predictor for obtaining disease control, monitoring early change in CEA level might be useful due to high sensitivity and positive predictive value, in spite of low specificity for detection of PD patients. No significant financial relationships to disclose.