Prognostic Value of the Combination of Circulating Tumor Cells Plus KRAS in Patients With Metastatic Colorectal Cancer Treated With Chemotherapy Plus Bevacizumab

Objective Circulating tumor cells (CTCs) and v-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog (KRAS) status were identified as prognostic factors for progression-free survival (PFS) and overall survival (OS) in patients with metastatic colorectal cancer treated with chemotherapy and bevacizumab in analyses of the MACRO (Maintenance Treatment in Advanced Colorectal Cancer) trial. In this post hoc analysis of the MACRO trial, the potential additive effect of these 2 factors on patient outcomes was explored. Methods A total of 158 of the 480 patients involved in the MACRO trial were included in the biological marker substudy. CTC isolation and enumeration were centralized and performed using the CellSearch System (Veridex LLC, Raritan, NJ) in 7.5 mL of whole blood. Evaluation of KRAS status was performed retrospectively by the standard method used at each center. PFS and OS were analyzed by the Kaplan–Meier method according to CTC count and KRAS status. Results Patients with < 3 CTC per 7.5 mL blood at baseline and KRAS wild-type tumors had a median PFS of 14.2 months compared with 6.2 months in patients with ≥ 3 CTCs and KRAS mutated tumors (P < .0001; hazard ratio, 3.0; 95% confidence interval, 1.8-5.2). Similar findings were observed for OS (28.9 and 13.7 months, respectively, P = .0004; hazard ratio 2.8; 95% confidence interval, 1.6-4.9). Multivariate analyses showed that CTC count ≥ 3 and KRAS status were the only independent prognostic factors for both PFS and OS. Conclusions This post hoc analysis showed that CTC count and KRAS status were independent prognostic factors for outcomes in patients with metastatic colorectal cancer treated with bevacizumab ± chemotherapy. These factors should be taken into account in the design of future phase III trials.