Circulating tumor cells (CTC) predict progression free (PFS) and overall survival (OS) in patients with metastatic colorectal cancer

Abstract

4010 Background: Treatment options for patients with metastatic colorectal cancer (mCRC) have recently expanded. However, the introduction of new regimens has highlighted the need for biomarkers to guide and monitor therapy. This study investigates the hypothesis that CTC levels can predict clinical outcomes in patients with mCRC. Methods: In a prospective multi-center study, 7.5 mL of blood from 456 patients with mCRC were tested for CTC using immunomagnetic separation before starting 1st, 2nd or 3rd line therapy and at subsequent radiographic follow-up timepoints. Response on imaging was determined by participating centers. Results: Patients were stratified into unfavorable and favorable prognostic groups based on levels of =3 or <3 CTC per 7.5mL, respectively. Median PFS, OS and significance between the two groups (log rank test) at different timepoints after the initiation of therapy is indicated in the table . The OS of patients converting to or maintaining unfavorable CTC at follow up timepoints was worse than for patients maintaining favorable CTC (12.6, 7.0 vs. 21.1 months, respectively, p<0.0001). In multivariate analyses, which included age, ECOG performance status, and the line and type of therapy, CTC remained the most significant independent predictor of outcome. Conclusions: CTC levels before treatment and at subsequent timepoints are an independent predictor of PFS and OS in patients with mCRC. CTC levels of =3 per 7.5mL of blood after initiation of therapy are highly predictive of shorter PFS and OS. A large randomized phase III study to confirm these findings in mCRC patients receiving first line therapy recently completed accrual (DCCG CAIRO- 2). [Table: see text] No significant financial relationships to disclose.