The role of circulating tumor cells and K-ras mutations in patients with locally advanced rectal cancer: a prospective study

Rectal cancer is a common malignancy with a relatively poor prognosis. We assessed the possible prognostic and predictive role(s) of circulating tumor cells (CTCs) and K-ras mutations in locally advanced rectal carcinoma (LARC) patients. CTCs number and K-ras mutation status were assessed in the Peripheral blood and tumor tissue samples of 60 patients with LARC compared to control group (normal rectal mucosa). Data were correlated to relevant clinico-pathological features, response to treatment, disease free (DFS) and overall survival (OS) rates. K-ras mutations were present in 24/60 (40%) patients. Baseline CTCs (< 5 cells/7 ml blood) were detected in 23/60 (38.3%) patients, and 37 (61.7%) had baseline CTCs (≥ 5 cells/7 ml) blood (P = 0.071). Serial sampling showed a decrease in CTCs levels in 40 (66.7%) patients and increase in 20 (33.3%) patients (P = 0.01). Patients with K-ras mutations had a significantly poor response to treatment, with reduced DFS and OS rates (P = 0.001, 0.004, and 0.001; respectively). Similarly, decreased CTCs levels during treatment associated significantly with better pathological responses (P = 0.003). Multivariate analysis demonstrated that K-ras mutation and baseline CTCs are independent prognostic factors for DFS (P = 0.014 and 0.045; respectively) and OS (P = 0.002 and 0.045; respectively). The presence of mutant K-ras and baseline CTCs ≥ 5 cells associated significantly with poor pathological response, shorter DFS and OS rates compared to those with either K-ras mutation or CTCs ≥ 5 cells only (P = 0.014, 0.005 and 0.001, respectively). K-ras mutations, baseline and serial CTCs changes represent good prognostic and predictive factors for LARC patients.