Tracking Mutations in Cell Free Tumour DNA to Predict Relapse in Early Colorectal Cancer

TRACC Part B: Despite potentially curative surgery +/- adjuvant chemotherapy, a proportional of patients with early stage CRC will experience disease relapse. Current tools for surveillance, e.g., blood sampling for tumour markers (CEA) are neither sensitive nor specific. We hypothesise that detection of mutations in circulating free DNA (cfDNA) in plasma can predict relapse in patients with early stage CRC. Circulating cell free tumour DNA (ctDNA) maintains the same mutations that are present in tumour. In colorectal cancer CRC, primary tumours and\& metastases exhibit high genomic concordance. Therefore the TRACC study TRACC Part B is investigating whether serial blood samples taken from in patients with stage II and III fully resected early stage CRC colorectal cancer that have undergone potentially curative surgery, blood samples to can be used to detect and\& quantify ctDNA may in order to identify minimal residual disease MRD and predict relapse earlier than existing methods. CtDNA may ultimately help identify a subset of patients that are or are unlikely to benefit from adjuvant chemotherapy and could therefore safely spare some patients from receiving unnecessary chemotherapy \& its associated side-effects. TRACC Part C: We hypothesis that ctDNA guided adjuvant chemotherapy administration will enable biomarker driven selection of patients who would and would not benefit from adjuvant chemotherapy and thereby reduce the proportion of patient receiving unnecessary adjuvant chemotherapy, reducing the potential side effects associated with it, but without compromising disease free survival (DFS). : This part of the study will use tThe blood test ctDNA result from a post-operative blood sample willto guide adjuvant chemotherapy treatment decisions. The study aims to demonstrate that athe de -escalation strategy of ctDNA guided adjuvant chemotherapy is non-inferior to standard of care treatment as measured by 3 year DFS in patients with high risk stage II and stage III CRC, in those who have no evidence of MRD (ctDNA negative). after surgery for patients with colorectal cancer who are following the standard of care pathway. Patients are randomised at the post- operative time point to: Arm A (standard of care adjuvant chemotherapy), or Arm B (ctDNA guided adjuvant chemotherapy) arm. For the ct DNA guided arm, patients who are ctDNA negative at this time point will have their chemotherapy de-escalated.