Utility of Cell-free Tumour DNA for Post-surgical Follow-up of Colorectal Cancer Patients

While efficient surgical treatment is the key to prolonged survival of patients with colorectal cancer, post-surgical follow-up is important for the early detection of relapsing disease or of disease progression. Current dispensarization, typically based on imaging CT, PET, MR, is frequently supported by the observation of tumour markers (CEA, CA19-9). Due to their limited sensitivity and selectivity, better tools for monitoring of the disease are desirable. Tumour cell-free DNA (cfDNA) has been recently demonstrated as a new promising molecular marker for observation and early detection of disease progression. We present results of post-surgical monitoring tumour cfDNA in the cases of seven patients suffering from advanced forms of CRC. We applied a mutation-based approach in which the total cfDNA was screened for a specific somatic mutation present in the primary tumour. We screened a panel of the most frequent somatic mutations covering the genes APC, KRAS, TP53, PIK3CA and BRAF. All patients were tested positive for tumour cfDNA prior to surgery. cfDNA was then evaluated within a week after surgery and subsequently in monthly intervals. We present typical cases of colorectal cancer patients who underwent surgical treatment at different levels of radicality with or without adjuvant chemo/biotherapy. The tumour cfDNA status was found to be always closely correlated with the actual clinical status of the patient. The cfDNA appears to be a viable tool for the monitoring of the clinical progression of CRC in patients with cfDNA positivity prior to surgery.