Accurate Allocation of Completion Resection in Early Colorectal Cancer

After introducing a nationwide screening program for colorectal cancer (CRC) in Denmark, more cases of early-stage CRC are being detected. Cancers in the earliest stages are often removed locally, either during the diagnostic colonoscopy or through planned minimally invasive surgery.
This early detection of cancer, and thereby an improved prognosis, is a positive feature but has also introduced a new clinical dilemma. Is the patient fully cured by the local resection, or do they need further surgery? Whether further surgery is recommended at the Multi-Disciplinary Team (MDT) board meeting depends on the outcome of specific criteria from the histopathological assessment of the locally removed specimen.
The presence of these criteria does not, however, translate directly into the presence of residual disease - merely into a theoretically increased risk. In Denmark, after surgery, the fraction of cases with residual disease has been around 15% for many years. In the remaining 85% of cases, local removal alone was curative - and the surgery appears excessive.
Investigating blood samples for the presence of circulating tumor DNA (ctDNA) is a new and promising method for cancer detection. The method utilizes that cancer cells release ctDNA into the circulation. ctDNA detected in blood drawn from a patient a few days after local removal of a tumor indicates that residual disease is present and further treatment, such as surgery, is needed.
The purpose of this study is to investigate, whether analyses of ctDNA can correctly identify patients with residual disease after local removal of early CRC. If this identification proves accurate, many patients can be spared further surgery.