Carcinoembryonic antigen kinetics predict response to first-line treatment in metastatic colorectal cancer: Analysis from PRODIGE 9 trial.

BACKGROUND: To examine the relationship between carcinoembryonic antigen (CEA) kinetics and prognosis in metastatic colorectal cancer (mCRC) patients receiving first-line chemotherapy in the PRODIGE9 trial. METHODS: Associations between monthly CEA measurements within 6 months since baseline and progression-free survival (PFS) were evaluated using a joint-latent class-mixed model. A validation set was used to test our prognosis model. Correlations between CEA trajectories (classes) and baseline characteristics were also investigated. RESULTS: Three classes were identified. Class 1 had low baseline CEA with small variations. Class 2 had high baseline CEA with a rapid decrease reaching the same CEA level at 6 months as in class 1. Class 3 had high baseline CEA with a transient decrease followed by an increase to reach, at 6 months, the same CEA level as at baseline. Six-month PFS was significantly lower in class 3 than in classes 1 and 2 (57% vs. 91% and 93% respectively; p<0.01). Class 3 was significantly associated with ECOG 2 status, a high LDH level and non-resected primary tumor. DISCUSSION: Variations in CEA kinetics correlate with prognosis in patients receiving first-line chemotherapy for mCRC. We propose here a user-friendly application to classify CEA trajectory.