Is CA 19-9 a lagging indicator? How is it used?

My mom's CA 19-9 has been all over the place since her diagnosis over 5 years ago. It is worth noting that this test is merely a tool and not definitive. For instance, those with fatty liver or inflammation can have higher CA-19-9 numbers. There are other things that can cause this test to jump around. What counts is the trend. If the trend is consistently upwards, it's a good indicator of PC.

There is a new test called Signatera which is a like a blood biopsy able to find cancer cells in the blood. I recommend this test to anyone searching for a clearer indication of whether they have cancer in their blood. But, as any skilled oncologist will tell you, the scan tells the story. Blood tests are not always accurate.

My husband has done 9 months of Gem-Abraxane and our oncologist is not stopping. His PET scans had been clear for 9 months (or since surgery over a year ago - depending on which dcotor or radiologist we listen to) but like @juneday said, the cancer cells could be 'hiding'. Chemo is depressing but if it keeps the cancer under control, my husband and I will stick to the course our oncologist has charted.

Go back on the chemo. Been there. Done that & was not wanting to go back on chemo. You may be able to stop it again when the numbers trend within normal limits again. I have been back on since May and in October finally got to 29.4; had pneumonia; shot up to 93.9 & 105.2 & just now on Jan 2. started to trend down to 82.4! Hoping that will continue so I can look forward to another time when I can stop for a while 🙂

For me, the imaging is the lagging indicator and CA19-9 is the leading indicator that cancer may be processing (though it can be due to inflammation also). Images lagging in MY case as it takes awhile, relative to growth, what one can see in an image. CA19-9 is an antigen, I believe; so its specifics differ according to internal responses.

My radiation oncologist told me that they can’t see the cancer unless there’s 50,000 thousand in one place

Personally, I am a fan of the CA 19-9 marker, I had a Whipple procedure in 2018. Cancer returned in 2023 and the CA 19-9 marker increased steadily tracking the Pancreatic Cancer. After successful stereotactic radiation treatment the marker decreased to below 34. Last year in 2024 my markers started increasing again and again a pet scan showed that it had returned. I am currently undergoing chemotherapy and after one month, the CA 19-9 marker decreased from 1500 to under 500. For me, the marker has been 100% reliable on tracking the state of my pancreatic cancer. I do agree with the comments here that say you have to get a trend line and one test may not mean anything unless it’s really high. God bless you and I pray for your recovery. 🙏🏼

I had read on this site and my doctors seem to agree that CA19-9 is not a test that locks in that you have cancer. There are other things that can cause high numbers like infection. I had low BP 70/40 and fever. CA19-9 was 1303. A scan is what show if for sure you have cancer, or it is something else. In my case the CT scan show an inflamed and infected ascending large colon. After IV antibiotics and other treatments I could remember, and my BP was back up in normal range. I had sepsis and blood culture showed infection. Weeks post hospital stay for this my CA 19-9 was back down to 55. To me this indicates that even extremely high CA 19-9 numbers can be caused something other than cancer. Best wishes to all.

My mom also just had a recurrence after nearly five years - it’s encouraging for me to hear that you’re here and doing well two years post recurrence! Where was your recurrence located?

The recurrence was in the mesentery exactly where the head of my pancreas used to be before the Whipple surgery.

yes