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

Background: There have been no reports evaluating the utility of monitoring early change in serum carcinoembryonic antigen (CEA) level as a predictor for subsequent radiological response to gefitinib in patients with non-small cell lung cancer. In this report, we investigated its role using the data from 110 non-small cell lung cancer (NSCLC) patients.

Methods: The daily rate of CEA change was defined as: (M0-Mx)/Dx/M0x100(%), using the baseline level (M0), the level on day X (Mx), and the number of days from day 1 to day X (Dx).

Results: The daily rate of CEA change until confirmation of an objective response was significantly higher in patients with an objective response or stable disease than progressive disease (PD) patients (p < 0.0001). Receiver operating characteristic analysis revealed that a cut-off level of 0.58% increase most accurately reflected tumor shrinkage, with sensitivity and specificity for disease control of 89.1% and 73.3%, respectively. In 41 (37%) patients, CEA was reassessed within the first two weeks after day 1. The daily rate of CEA change in this early phase tended to vary with the response (p = 0.0975), and reflected disease control less precisely, with sensitivity and specificity of 82.1% and 40.0%, respectively when a cut-off of 0.58% increase was used.

Conclusion: The extent of CEA change until confirmation of an objective response correlated significantly with tumor burden. Monitoring an early CEA change, however, did not seem to be useful for detection of PD patients because of the low specificity. Considering the relatively high sensitivity, this model might be helpful for detecting those in whom subsequent disease control is likely.