When my endometrial cancer recurred, I talked my oncologist into letting me get the Foundation Medicine liquid biopsy, because I was hoping to see if the new tumors had the same mutation profile as the initial tumor. I didn't manage to talk him into it until the day of my first chemo treatment, so I didn't actually get the blood drawn until right before the second chemo treatment. This test did not detect any of my tumor mutations AT ALL. When I had a CT scan after the third cycle, the tumors had only shrunk marginally, so it wasn't because the chemo had killed everything. I'm a molecular biologist, so I got Foundation Medicine to send me the raw sequence data, and there really was absolutely zero sign of my tumor in the data. So my personal experience is that liquid biopsies are not sensitive enough to be good for anything. But some tumors seem to shed more DNA than others.

Also, the people in the pancreatic cancer forum on this site have experience with the Signatera liquid biopsy, which should be more sensitive than FM. They seem to think that the Signatera test comes up positive well after their CA19-9 starts rising. So even that doesn't really live up to the hype.

Do you know if you have high CA125 when you cancer is present? Mine is only somewhat high, but I'm still finding the test very useful at gauging whether the clinical trials that I've been on are working. But my oncologist never would have ordered it himself. I asked for it. If I ever get to NED status, I'm going to try to get frequent CA125 tests.