Circulating Tumor DNA (ctDNA) – A Potential Adjunct to FDG-PET Imaging in Cancer Follow Up (RSNA 2019, Sun Dec 01 – 06)

TEACHING POINTS

• With the continuous advances in healthcare – Next Generation Sequencing and PET-CT are revolutionising cancer diagnostics

• Survival outcomes in cancer can be improved by early detection of metastatic disease or relapse during follow up

• Next Generation sequencing is an extremely high end modality wherein hundreds to millions of DNA molecules are sequenced in parallel

• CtDNA is an application of NGS to monitor the amount of tumor specific DNA in the peripheral blood of patient

• Using ctDNA, a non-invasive investigation, to monitor the remission status can potentially reduce the frequency of imaging required at follow up, hence reducing the side effects and discomfort

• According to Wong R et al, for colorectal cancer patients with indeterminate findings on routine investigations, ctDNA detection increases the probability that the findings indicate metastatic disease, including in a nonpredefined subset that also underwent FDG-PET imaging

• Hence, using ctDNA as an adjunct to FDG-PET imaging during cancer follow-up seems to be an acceptable proposition.

TABLE OF CONTENTS/OUTLINE

• What is ctDNA? How is it measured?

• What are the current guidelines for cancer follow up?

• Review of literature • Advantages and limitations of FDG-PET imaging

• Advantages and limitations of ctDNA

• Conclusion