ASCO GI 2022 | Using CTCs to determine minimal residual disease in GI cancers

Scott Kopetz, MD, PhD, The University of Texas MD Anderson Cancer Center, Houston, TX, outlines the impact circulating tumor cells (CTCs) are making for gastrointestinal cancers empowered by the significant improvement in next-generation sequencing (NGS) methodologies. NGS allows for the detection of microscopic amounts of tumor DNA found in patients. Many NGS approaches sequence the primary tumor and search for specific alterations present in the plasma of patients to determine whether any disease remains following treatment. Such techniques allow for high positive predictive value and as such if CTCs are discovered in a patient there is a high probability that the cancer persists. Early studies are focusing on whether the delivery of adjuvant therapy can be improved using CTC detection. For some patients following surgery, microscopic amounts of disease may be left behind which a CT scan may be unable to detect. However, such microscopic amounts of disease may be found via the detection of circulating tumor DNA. On the other hand, there is the issue of overtreating patients. Many patients with stage III colon cancer can be treated with surgery alone, sparing the toxicities associated with chemotherapy. CTC detection can help uncover which patients require chemotherapy. Dr. Kopetz explains how the detection of the cancer before it appears radiographically in patients who had undergone adjuvant chemotherapy and surgery is the area in which CTCs are generating the most impact. Using CTCs the cancer may be detected before it reaches a point in progression where it can be seen radiographically. This interview took place at the American Society of Clinical Oncology (ASCO) Gastrointestinal Cancers Symposium.