Background
The Maintenance in Colorectal Cancer trial was a phase III study to assess maintenance therapy with single-agent bevacizumab versus bevacizumab plus chemotherapy in patients with metastatic colorectal cancer. An ancillary study was conducted to evaluate the circulating tumor cell (CTC) count as a prognostic and/or predictive marker for efficacy endpoints. Patients and
Conclusions
The CTC count is a strong prognostic factor for PFS and OS outcomes in metastatic colorectal cancer patients.
Methods
One hundred eighty patients were included. Blood samples were obtained at baseline and after three cycles. CTC enumeration was carried out using the CellSearch® System (Veridex LLC, Raritan, NJ). Computed tomography scans were performed at cycle 3 and 6 and every 12 weeks thereafter for tumor response assessment.
Results
The median progression-free survival (PFS) interval for patients with a CTC count ≥3 at baseline was 7.8 months, versus the 12.0 months achieved by patients with a CTC count <3 (p = .0002). The median overall survival (OS) time was 17.7 months for patients with a CTC count ≥3, compared with 25.1 months for patients with a lower count (p = .0059). After three cycles, the median PFS interval for patients with a low CTC count was 10.8 months, significantly longer than the 7.5 months for patients with a high CTC count (p = .005). The median OS time for patients with a CTC count <3 was significantly longer than for patients with a CTC count ≥3, 25.1 months versus 16.2 months, respectively (p = .0095). Conclusions: The CTC count is a strong prognostic factor for PFS and OS outcomes in metastatic colorectal cancer patients.