Hey, radiologist here. So, the question of "what next" after a positive result on one of these tests is still... open. The Grail test provides indication of li

Hey, radiologist here. So, the question of "what next" after a positive result on one of these tests is still... open. The Grail test provides indication of likely tissue of origin, so a likely first step may be a targeted study (e.g. colonoscopy if it said a colonic source, MRI if it said pancreatic). There may be role for PET/CT as well to further stage and assess for metastases, perhaps after finding a lesion. What to do if your blood test is positive but the workup is negative? Lots of discussion but nobody is quite sure. As for a periodic full body MRI, I will say that currently uh, most of those are garbage. Unfortunately, for a full body MRI to be practical (that is, to not take hours and hours), you have to run very few sequences. (For example, a dedicated MRI of say, your brain or your liver alone could take about hour, each.) As a result, you greatly reduce your sensitivity for most pathologies, which kind of is counter to the point of the MRI to begin with.