Short summary

It is conceivable that tumor DNA in the blood is detectable earlier than recurrence of cancer on imaging and therefore is applicable as a guide in relation to recurrence or progression of cancer.

The aim of this study is to investigate if methylated ctDNA constitutes an important tool for the follow-up of patients who have undergone resection or other local treatment of liver metastases from colorectal cancer. By detecting ctDNA in the blood or displaying its dynamics before it would be visible on a CT scan, recurrence can possibly be detected earlier and active treatment initiated.

Rationale

Colorectal cancer is a disease with significant morbidity and mortality. Around 4900 people are yearly diagnosed with colorectal cancer in Denmark. The overall 5-year survival rate is 55-60 %.

Around 70% of the patients can undergo surgery with curative intent  Depending on stage and prognostic factors a group of patients are offered adjuvant chemotherapy. At the time of the diagnosis 20-25% of the patients have synchronous metastases and another 20-25% develop metachronous metastases. Some patients with liver metastases, which is the most common site, and to a lesser extent patients with lung or peritoneal spread, may be treated with curative intent if the metastases are resectable - either up front or after downsizing with chemotherapy depending on risk factors. If tumor shrinkage is achieved by chemotherapy, patients may be offered local treatment of the liver metastases; either resection, radiofrequency ablation or radiotherapy. Patients who have undergone liver resection or radiofrequency ablation are often offered adjuvant chemotherapy.

Imaging, commonly computed tomography (CT) scan of the thorax and abdomen, is the gold standard for evaluating treatment response based on the Response Evaluation Criteria in Solid Tumors (RECIST), but it has disadvantages in non-measurable disease. Furthermore, objective progression according to RECIST requires not only treatment resistance but also substantial increase in tumor size or new lesions. Finally, some patients may have delayed access to other potentially more effective treatment.

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. Plasma as a liquid biopsy facilitates analysis of repeated samples by a minimally invasive technique allowing treatment monitoring during the whole treatment course.

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. A few studies indicate that it is applicable for monitoring the effect of chemotherapy of metastatic colorectal cancer and follow-up after curatively intended treatment.

The present study aims at investigating the clinical utility of NPY meth-ctDNA for follow-up after curative intent treatment of metastatic colorectal cancer.

Description of the cohort

The study is a prospective, observational biomarker study. 37 patients at the Department of Oncology, Vejle hospital, with metastatic colorectal cancer, who are offered localized treatment of liver metastases will be included.

Data and biological material

Longitudinal blood samples

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