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Comment & Response
April 2, 2020

Circulating Tumor DNA as a Prognostic Marker in Stage III Colon Cancer—Reply

Author Affiliations
  • 1Division of Personalised Oncology, Walter and Eliza Hall Institute of Medical Research, Melbourne, Victoria, Australia
  • 2Department of Medical Oncology, Western Health, Melbourne, Victoria, Australia
  • 3Department of Oncology, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia
  • 4Faculty of Medicine, Dentistry and Health Sciences, University of Melbourne, Melbourne, Victoria, Australia
  • 5Ludwig Center for Cancer Genetics and Therapeutics, Johns Hopkins University School of Medicine, Baltimore, Maryland
JAMA Oncol. Published online April 2, 2020. doi:10.1001/jamaoncol.2020.0289

In Reply We thank Zhao et al for their comments on our article1 and appreciate the opportunity to further discuss the value of circulating tumor DNA (ctDNA) analysis, focusing on 3 points raised by Zhao and colleagues. First, there is a fundamental difference between postoperative ctDNA and conventional prognostic markers.2 The presence of ctDNA indicates that the administered therapy (be it surgery, chemotherapy, radiotherapy, or immunotherapy) has not eradicated all cancer cells. For patients in whom the primary tumor was removed by surgical resection, the continuous presence of ctDNA means that millions of actively dividing cancer cells are present at occult metastatic sites within the body.

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