CAPhO Connections Podcast: Liquid Clues: Decoding circulating tumor DNA (ctDNA) to Rewriting Colorectal Cancer Care

Author/Presenter
Stacey Cohen
Category
Podcast
Year Created
2026
Details

This episode explores the evolving role of circulating tumour DNA (ctDNA) in reshaping colorectal cancer care and how detection of tumour-derived DNA fragments in plasma is challenging traditional reliance on imaging, pathology, and CEA for assessing disease burden and recurrence risk.

We unpack what ctDNA represents biologically, including its role in identifying minimal residual disease and emerging actionable alterations, as well as its strengths and limitations in clinical interpretation.

The discussion highlights how ctDNA is already influencing practice, from early detection of recurrence risk shortly after surgery to guiding surveillance strategies and managing cases where ctDNA is positive despite negative imaging, raising important questions about how success is defined in curative-intent treatment and when to act on molecular signals.

We also examine real-world barriers to feasible adoption, alongside the rise of early-onset colorectal cancer and shifting screening thresholds in Canada.

Overall, the episode highlights an emerging era of precision oncology where multidisciplinary teams come together to turn ctDNA signals into earlier answers, clearer decisions, and more proactive cancer care.

Learning Objectives

After this episode, listeners will be able to:

  • Understand what ctDNA is and why it is transforming how we detect and define colorectal cancer recurrence earlier than ever before.
  • Explore how ctDNA is reshaping real-world colorectal cancer care, from post-surgical surveillance to guiding treatment decisions alongside imaging and CEA.
  • Examine how to interpret ctDNA results in practice, including discordant findings and what they mean for disease activity, risk, and treatment.
  • Discuss the growing role of ctDNA in precision oncology, including actionable mutations, treatment adaptation, and minimal residual disease monitoring.
  • Identify current barriers and future opportunities for ctDNA adoption, including turnaround time, access, cost, rising early-onset CRC, and multidisciplinary collaboration in advancing care.

About the Author: Stacey Cohen

Dr. Stacey A. Cohen is a Professor at the Fred Hutch Cancer Center and University of Washington. She is a GI medical oncologist, with a clinical practice that focuses on lower GI cancers. She is the co-director of the Colorectal Cancer and Peritoneal Malignancy (HIPEC) multidisciplinary clinics. Her research focuses on biomarkers of prognosis and treatment response, with a special focus on circulating tumor DNA (ctDNA).

Dr. Cohen

 

 

 

 

Resources Used:

  1. Hakrabarti, S., Cohen, S. A., Tin, A., et al. (2026). Utility of circulating tumor DNA to assess tumor response in patients with locally advanced rectal cancer undergoing neoadjuvant therapy. Cancers, 18(4), 589. https://doi.org/10.3390/cancers18040589
  2. Cohen, S. A., Liu, M. C., & Aleshin, A. (2023). Practical recommendations for using ctDNA in clinical decision making. Nature, 619(7969), 259–268. https://doi.org/10.1038/s41586-023-06225-y
  3. Gottschalk, Z., & Cohen, S. A. (2024). Use of circulating tumor DNA to guide decision-making in adjuvant colon cancer. Current Oncology Reports, 26(8), 959–966. https://doi.org/10.1007/s11912-024-01565-y
  4. Gottschalk, Z., Redman, M. W., Baker, K. K., Gigic, B., et al. (2025). Comparison of risk factors, treatment strategy, and outcomes of early- vs. older-onset colorectal cancer within the prospective ColoCare study. Journal of Clinical Oncology, 43(4_suppl), 95. https://doi.org/10.1200/JCO.2025.43.4_suppl.95
  5. Heit, M., & Cohen, S. A. (2025). Contemporary use of ctDNA for the colorectal surgeon. Clinics in Colon and Rectal Surgery, 38(5), 334–338. https://doi.org/10.1055/s-0044-1801379
  6. Hsieh, R. W., Symonds, L. K., Siu, J., & Cohen, S. A. (2025). Identification of circulating tumor DNA as a biomarker for diagnosis and response to therapies in cancer patients. International Review of Cell and Molecular Biology, 391, 43–93. https://doi.org/10.1016/bs.ircmb.2024.08.006
  7. Rajdev, L., King, G. G., Lieu, C. H., Cohen, S. A., Pant, S., et al. (2025). Incorporating circulating tumor DNA testing into clinical trials: A position paper by the National Cancer Institute GI Oncology Circulating Tumor DNA Working Group. JCO Precision Oncology, 9, e2400489. https://doi.org/10.1200/PO-24-00489
  8. ⁠⁠https://pubmed.ncbi.nlm.nih.gov/37438589/⁠⁠
  9. ⁠⁠https://ascopubs.org/doi/abs/10.1200/PO-24-00489⁠⁠