[didgeoridoo]

> If you’re looking for cancer in the blood, you’re probably too late as this suggests metastatic spread.

Isn’t the point of cfDNA that you can pick up “dead” DNA fragments floating around long before you have viable cancer cells drifting through the bloodstream and lymphatic system?

[mbreese]

Yes. Normal cells break apart all the time. If you measure total cfDNA amount in a blood sample, you'll find significantly a higher cfDNA concentration after you exercise. It's a normal part of the wear and tear of cells.

So, if you find cfDNA from a tumor, it's not necessarily indicative of metastatic spread... just that the tumor cells have been broken up. It could be from too much growth, or immune attack, or metastasis, or... etc.

cfDNA is great in that you can run a single assay to cover the entire body. cfDNA is difficult because your single assay covers the entire body. You can't localize the source of cfDNA.