The role of tumor markers and biomarkers in colorectal cancer.

A steady increase in colorectal cancer (CRC) incidence and mortality has been observed in Europe, despite the continuous advancement in diagnostic and therapeutic methods. Accordingly, further progress is very much desirable in non-invasive diagnostic methods to enable early diagnosis, preand postoperative staging, and to assist in selecting the most suitable neo-adjuvant and adjuvant therapeutic methods and post-treatment follow-up. This review summarizes the current state of knowledge about the role of tumor markers and biomarkers in CRC diagnosis, treatment and follow-up. New biomarkers which are absent in healthy persons and present in CRC are still being investigated, especially those that can be detected at early development stage of the disease and used in screening tests. Unfortunately, no molecule that would meet all of the foregoing criteria has been identified so far. Carcinoembryonic antigen still remains the only tumor marker of recognised efficacy in monitoring patients during and after CRC therapy. Clinical studies and retrospective analyses allowed to discover and introduce to the clinical practice several bioindicators that assist in selecting the proper chemotherapeutic drug. There are attempts to "personalise" chemotherapy based on presence or absence of specific biomarkers. Therapy with anti-EGFR antibodies is desirable in patients with advanced CRC and absence of KRAS or BRAF mutation. Defining tumor phenotype - microsatellite instability (MSI) or microsatellite stability (MSS) and testing for the presence or absence of 18q chromosome deletion is very much desirable in standard 5-FU-based therapy. Analysis of UGT1A1 alleles may be the basis for modified dosing and reducing the potential toxicity of irinotecan. Studies on CRC biomarkers need to continue to closely examine the relationship between therapy and CRC curability. Targeted therapy against membrane receptors appears to be the future of CRC therapy.