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MEDOCC: Determining the prognostic value of ctDNA in patients with stage II and III colorectal cancer

Colorectal cancer recurrence after surgery

Almost all patients with colorectal cancer, without metastases in other organs, have surgery to remove the tumor. Its purpose is to cure the patient. In some patients, the disease returns at some point. In these patients, colon cancer cells remained somewhere in the body after the surgery. These colon cancer cells are too small to be visible on CT scans. To kill these remaining cancer cells, some of the patients receive chemotherapy after the surgery. Problem is, that we just don't know exactly who we should and who we should not give chemotherapy. In the MEDOCC study, we look at whether we can use circulating tumor DNA to predict which patients will benefit from additional chemotherapy and which patients do not need it.

What is Circulating Tumor DNA?

Our body consists of billions of cells. These cells contain DNA, our hereditary material. A cancer cell also contains DNA. This DNA differs from the DNA of normal, i.e. benign, body cells. All cells secrete DNA, which can be found in the bloodstream. Due to new techniques we are now able to trace DNA that comes from cancer cells in a patient's blood.

What is the aim of the MEDOCC study?

The idea is that cancer cells have remained in the body in patients whose colorectal cancer recurs within a few years after surgery. These remaining cancer cells might release DNA into the bloodstream. The aim of the MEDOCC study is to determine whether we can detect this 'circulating tumor DNA' in colorectal cancer patients shortly after surgery. And if so; whether colorectal cancer does indeed recur in those patients. We also assess at various other time points whether circulating tumor DNA is detectable in the blood of patients, namely before surgery and 6, 12, 18, 24 and 36 months after surgery. We hope this will enable us to better determine in the future which patients will benefit from additional chemotherapy after surgery and which patients will not. The MEDOCC study started in 2016.

Who can participate in the MEDOCC study?

Patients with colorectal cancer who are undergoing surgery and who do not have metastases in other organs can participate in the MEDOCC study. A patient cannot participate without participating in PLCRC, and if he/she is treated with radiation or chemotherapy before surgery. It is important to know that the extra blood drawn is not analyzed for the presence of circulating tumor DNA immediately. This will only happen at a later time point. We use the clinical data we collect in PLCRC for the analysis..

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