How would you approach a stage II colon cancer with negative ctDNA but markedly elevated CEA level post-colectomy?  

Thanks for the question. Highly complicated case. Few things matter here. First, what platform is used for ctDNA testing (whether tumor informed or not), and second whether this is T4 or T3 disease. It would be unusual to have high CEA but negative ctDNA in a true minimal residual disease (MRD). For...

Agree with the above. Re-staging scans, and full colonoscopy if not done. Is it uptrending? How long since surgery was it checked? Smoker? If female, are they up to date on mammograms?  I wouldn’t make adjuvant treatment decisions based on the CEA alone but still use our usual guides for...

Agree with the answers above, but always important to remember ctDNA has potential false negative rates as a single post-operative value even in a tissue based assay has a low sensitivity. Some sites of metastatic disease also will not produce detectible ctDNA with current assays (lungs). I hav...

In a Cochrane analysis including 52 studies, the overall sensitivity of CEA ranged from 41% to 97% and specificity from 52% to 100%. Once a CEA threshold of 10 µg/L was applied, pooled sensitivity was 68% (95% CI 53% to 79%) and pooled specificity was 97% (95% CI 90% to 99%). Cochrane Database...

The question lacks enough details for a thorough response, but if CEA levels rose post-colectomy and ctDNA is absent, I'd suggest retesting ctDNA, as its detection sensitivity improves with subsequent tests. A PET scan could offer further insights. Sometimes, peritoneal carcinomatosis, which might n...