Short summary

It is conceivable that tumor DNA in the blood reflects the stage and severity of colon cancer and therefore is applicable as a parameter for a more precise pre-operative risk classification in order to select the right treatment for the right patient.

The aim of the study is to investigate if circulating tumor DNA as an adjunct to cTNM can predict post-operative risk of lymph node metastases and other risk factors in colon cancer patients. It may provide an approach for identifying patients to most likely benefit from neoadjuvant or adjuvant chemotherapy, closer monitoring and thus possibly improved survival.

Rationale

Colon cancer is a disease with significant morbidity and mortality. Around 3750 people are yearly diagnosed with colon cancer in Denmark. The overall 5-year survival rate is 65 %. 

The clinical (c) tumor, node, and metastasis (TNM) classification of colorectal cancer (Brierley 2017, 8th edition) is based on an overall assessment of clinical, endoscopic, and radiological findings before treatment and suggests the choice of treatment strategy. The pathological (p) TNM classification is based on all of the above, operative findings and the histopathological findings of surgical preparation. The disease stage, a synthesis of TNM into Union for International Cancer Control (UICC) stage I-IV, is determined by a multidisciplinary team of e.g. radiologists, surgeons and pathologists.

Around 80% of patients can undergo surgery with curative intent. Depending on stage and prognostic factors, a group of patients in stage II and III are offered adjuvant chemotherapy. 

A large number of patients are over-treated, especially in stage II, and biomarkers for refining the selection of patients for adjuvant chemotherapy are sought in the genetics and epigenetic characteristics. Despite adjuvant chemotherapy patients with locally advanced colon cancer still relapse and the disease represents a therapeutic challenge. Currently, neoadjuvant chemotherapy is not standard in operable colon cancer due to concerns as to tumor growth during treatment and inaccurate radiological tumor staging. 

Circulating tumor specific DNA (ctDNA) represents a relatively new marker that can be measured as a fraction of circulating total cell-free DNA (cfDNA). Droplet digital PCR with high sensitivity allows for detection of very small fractions of ctDNA. It has already been used in several studies on tumor specific mutations, and plasma analyses seem to give an overall relevant reflection of the tumor status. 

It is a disadvantage and limiting factor of measuring mutated DNA that not all somatically activating mutations are known in each cancer. This has increased the interest in the methylation of genes involved in epigenetic gene regulation. Aberrant methylation occurs in most malignant tumors and DNA hypermethylation in the regulatory regions of specific genes appear to be a potential marker measurable in plasma as methylated tumor specific DNA (meth-ctDNA). The neuropeptide Y gene (NPY) encodes a peptide in the central nervous system, which plays a role in many physiological functions. Hypermethylation of NPY (NPY meth-ctDNA) seems to occur in most colorectal cancers but not in normal colorectal tissue. 

The present study aims at investigating the clinical utility of NPY meth-ctDNA as an adjunct to cTNM for a more precise pre-operative risk classification of colon cancer in order to select the right treatment for the right patient.

Description of the cohort

The study is a retrospective biomarker analysis. It includes a hypothesis generating (N=100) and a validation cohort (N=100) of patients prospectively included in the "Syddansk Colorectal Cancer Database" at Vejle Sygehus.

Data and biological material

Blood

Collaborating researchers and departments

Department of Oncology, Vejle Hospital

• Associate professor Lars Henrik Jensen, MD, PhD
• Associate professor Torben Frøstrup Hansen, MD, PhD

Department of Immunology and Biochemistry, Vejle Hospital

• Molecular biologist Rikke Fredslund Andersen, PhD