Background: A possible correlation of disease progression and tumor stage in colorectal cancer patients with tumor-associated gene expression in disseminated tumor cells (DTC) was evaluated. Detection of DTC and expression of tumor-associated genes might be of clinical value with respect to individual patient prognosis, monitoring of therapy and as a surrogate tumor staging parameter.
Patients and methods: In a multicenter study, a total of 196 peripheral blood samples were collected from 76 patients with tumor stage Dukes' A to D and analyzed using a DTC detection assay consisting of immunomagnetic selection and expression analysis of the tumor-associated genes CEA, EGFR and GA733-2. DTC detection rates were assessed prior to surgery and post surgery in patients with tumor stage Dukes' A, B and C, and compared with results in metastatic patients. CEA serum protein levels were determined and compared with DTC and CEA expression, respectively.
Results: In a comparison analysis, EGFR and CEA expression was detected in 88% (p = 0.001) and 0% (p = 0.002) prior to surgery, in 66% (p = 0.001) and 20% (p = 0.002) post surgery, as well as in 15% (p < 0.0001) and 66% (p < 0.0001) of blood samples collected from metastatic patients, respectively. Expression of tumor-associated genes in DTC prior to surgery and in follow-up samples indicated an ongoing metastatic process. DTC detection rates in patients with Dukes' A (14%), Dukes' B (13%) and Dukes' C (40%) prior to surgery correlated statistically with the expected recurrence rate. There was no correlation between DTC expressing CEA and elevation of CEA serum protein levels.
Conclusion: EGFR and CEA gene expression correlated with disease progression and tumor stage. Detection of CEA expression in DTC might have a predictive value in colorectal cancer and may help to identify patients at a greater risk of relapse. DTC in peripheral blood collected prior to surgery as well as in follow-up samples have a prognostic clinical value.