Comparison of CAI5-3 and Carcinoembryonic Antigen in Monitoring the Clinical Course of Patients with Metastatic Breast Cancer1

Fifty-three women with metastatic breast cancer and serial plasma samples were selected to study the correlation between disease course and variations in circulating CAI5-3 and Carcinoembryonic antigen (CEA) levels. Forty-nine patients had their first sample drawn at the beginning of therapy, while four patients did not receive any treatment during the period of study. Clinical course was scored as progressive disease (PD), responsive disease (RD), and stable disease on the basis of radiological and physical evaluations. The percentage of variation in antigen level between the initial sample and samples drawn at the time of the clinical evaluation was correlated with clinical course. CAI5-3 levels above 22.0 units/ml and CEA levels above 3.0 ng/ml were considered elevated values. Antigen levels that increased >25% and decreased >25% from the initial value were considered to correlate with PD and RD, respectively. Vari ations in antigen levels ±25%from the initial value were considered to correlate with stable disease. Significantly more patients had elevated circulating levels of CA15-3 than CEA (96.2 versus 69.»%;P < 0.01) at some point in the course of disease. Overall, CAI5-3 correlated with disease progression, regression, or stability in a higher number of patients than CEA (60.3 versus 39.6%; P = 0.02). CAI5-3 increased >25% more often than CEA in patients with PD (75.0 versus 58.3%) and decreased 225V, more often than CEA in patients with RD (38.1 versus 23.8%). In a logistic regression model, changes in CAI5-3 levels correlated signifi cantly with both PD (/' = 0.0004) and RD (/' = 0.02), while changes in CEA levels did not (PD, P = 0.34; RD, P = 0.92). Furthermore, correlations obtained when using both antigens together failed to improve the results obtained with CA15-3 alone. The present study thus demon strates that CAI5-3 is more useful than CEA in monitoring the clinical course of patients with metastatic breast cancer.