Quantitation of response to therapy in patients with metastatic breast carcinoma by serial analysis of plasma gross cystic disease fluid protein and carcinoembryonic antigen.

The maximum percent change (MPC) of plasma carcinoembryonic antigen (CEA) and gross cystic disease fluid protein (CDP) were correlated with response to therapy in 92 metastatic breast carcinoma patients. In patients treated with hormone therapy MPC values were significantly different between patients with disease progression (Prog) and regression (Reg): MPC-CEA for Reg = -72 +/- 7%, for Prog = 396 +/- 150%; MPC-CDP for Reg = -86 +/- 6%, for Prog = 702 +/- 330%, P less than 0.001 in a one-way ANOVA for CEA and CDP. Similar differences were noted in patients treated with chemotherapy. Decreased (greater than 50%) plasma CEA levels were observed in 24/29 (83%) of Reg, 18/35 (51%) stable and 0/49 (0%) of Prog; decreased (greater than 50%) plasma CDP levels were noted in 19/24 (79%) of Reg, 21/28 (75%) of stable and 2/35 (6%) of Prog. Patients with plasma marker decreases greater than 50% had significantly longer responses to therapy (14.2 months for CEA, 14.1 months for CDP) compared to patients with less than 20% decrease (2.0 months for CEA, 0.8 months for CDP), P less than 0.001 in a one-way ANOVA. Decreasing marker levels during the initial six weeks of therapy (negative slope) accurately identified Reg or stable patients: the predictive value of a negative slope was 92% for CEA and 86% for CDP. Rising marker values correctly identified treatment failures (Prog): the predictive value of a positive slope was 90% for CEA and 76% for CDP. These data indicated that changes in plasma CEA and CDP levels reflected increasing or decreasing tumor burden during hormone or chemotherapy treatment of metastatic breast carcinoma. Criteria have been established to predict therapeutic outcome based on the slope of CEA or CDP after six weeks of treatment.U