The Association of Baseline Serum Tumour Markers with Outcome of Patients with Metastatic Colorectal Cancer Treated with Anti-EGFR Monoclonal Antibodies in the First Line

The measurement of serum tumour markers is a simple and non-invasive method for assessing the response to systemic therapies in metastatic colorectal cancer (mCRC) and estimation of prognosis. The aim of our retrospective study was to evaluate the association of baseline serum levels of carcinoembryonic antigen (CEA), carbohydrate antigen 19-9 (CA 19-9), thymidine kinase (TK) and tissue polypeptide specific antigen (TPS) with outcome of patients with mCRC treated with combination of chemotherapy and monoclonal antibodies against epidermal growth factor receptor (anti-EGFR mAbs) in the first line. In our study, the cohort included 102 patients treated with therapy based on anti-EGFR mAbs between years 2011 and 2017 at Department of Oncology and Radiotherapy, Medical School and University Hospital in Pilsen, Czech Republic. Serum samples were collected within one month before the initiation of treatment. In multivariate Cox analysis that included serum tumour markers and clinical baseline parameters show that high baseline serum CA 19-9 was significantly associated with worse progression-free survival (HR=1.871, p=0.0330) and also overall survival (HR=3.903, p=0.0006). We have not demonstrated association of baseline levels of CEA, TK and TPS with patients' outcome. CA 19-9 is commonly used serum tumour marker which is simple and readily available and its candidate prognostic importance in the setting of anti-EGFR therapy deserves to be studied in prospective trials.