ASCO GI 2022 | COBRA: ctDNA to help decide which patients with colon cancer will benefit from adjuvant chemotherapy

Van K. Morris, MD, The University of Texas MD Anderson Cancer Center, Houston, TX, outlines the investigation of circulating tumor DNA (ctDNA) as a predictive biomarker in adjuvant chemotherapy in patients with stage II colon cancer in the Phase II/III COBRA (NCT04068103) trial. Dr. Morris describes ctDNA as a powerful tool that can identify low volumes of disease quicker than traditional methods such as CT scans. ctDNA can be used as a prognostic biomarker for the presence of minimal residual disease (MRD) following the completion of definitive therapies. If ctDNA is not detected in a patient following therapy, their outcome is more favorable and they are less likely to develop recurrent disease whereas if ctDNA is detected then patients often experience eventual recurrence. However, there is no level 1 evidence thus far through prospective studies that demonstrate this technology as a predictive biomarker for whether patients will benefit from adjuvant chemotherapy. Therefore, the randomized Phase I/III trial is investigating the benefit of ctDNA detection in patients with resected stage II colon cancer, where patients will randomized 1:1 to either arm of the standard of care (SOC), that is observation, or ctDNA analysis. The trial will be using the Guardant Reveal test which incorporates colorectal cancer (CRC) specific somatic mutation profiling as well as unique epigenome methylation signatures. If patients are positive for ctDNA, they will receive 6 months of adjuvant chemotherapy. The primary endpoint of the Phase II stage of the trial is the clearance of ctDNA and in Phase III the primary endpoints will be disease-free survival (DFS) and recurrence-free survival (RFS). This interview took place at the American Society of Clinical Oncology (ASCO) Gastrointestinal Cancers Symposium 2022.