Thoughts on CA19 behavior close to nadir

@amiller7x7 thanks a lot this is very informative. On the last part of the graph, inside the green range I can see you had few upticks but trend in the first part was still going down before inverting. I wonder what was the amplitude of these upticks and how often you were testing. also out of curiosity why normal range was considered up to 54? wishing you good luck for next steps...

@peterello
Here's a plot of the 2025 data from CT scan in April (NED) to first routine CT scan (Jul 18) which occurred with metastatic recurrence on the CT scan. Our Oncology team relies more heavily on the CT scan for definitive diagnosis. This plot includes the most recent point showing an apparent acceleration in the rate of increase in CA19-9 values. We moved the CT scan to early next week and we expect to see tumor regrowth requiring a change in treatment. The small "upticks" were in the range of 1 to 10 units and tended to bounce around with no clear direction as opposed to the later data all of which were directionally increasing. As I mentioned, in our case, the trend lines were more important than any single data point. As to why the upper normal limit is 54, I have no direct knowledge of how that specific number was selected but it is the system used at the Fred Hutch Cancer Center in Seattle - I have to trust their calibration! :>)

@peterello
Forgot to mention that each point is a test - after the sharp rise in 2025, all samples done two weeks apart in answer to your question.

I would find this pattern much more reassuring than concerning. A CA 19-9 change from 56 to 61 is only about a 9% increase and, by itself, is not evidence that the chemotherapy has stopped working.

Your overall trend is:

466 → 573 → 481 → 326 → 273 → 139 → 108 → 90 → 56 → 61

That's roughly an 87% reduction from 466 to 61. More importantly, your CT is showing objective improvement: the pancreatic tumor decreased from 6 × 5 cm to 4 × 3 cm, the liver metastases are no longer visible, and the lung disease is stable or decreasing. Imaging generally carries considerably more weight than one small tumor-marker fluctuation.

CA 19-9 also doesn't have to behave like a smooth mathematical curve as it approaches its lowest level. There is no requirement that it gradually slow down before reaching a nadir or before eventually rising. It can plateau, fluctuate up and down, fall again, or remain relatively stable for some time. Inflammation, biliary issues, liver conditions and changes in blood-glucose control can also affect CA 19-9.

@amiller7x7 thanks a lot this is very informative. good look for the next scan and potential change in treatment... big hug.

@mcharlesfrancis unfortunately I took today another blood test after 4 weeks of chemo holiday and CA19 went from 61 to 69. we are still talking about relatively small increases but it's already two subsequent upticks. Haven't been careful with diet thought and my fasting glucose went from 105 to 160+ (have diabetes 2). this can potentially explain this second increase but two subsequent upticks are still strongly suspicious. Next week CT scan will hopefully tell.

The CT next week is much more important. ASCO specifically cautions that CA 19-9 should not substitute for imaging when assessing pancreatic cancer response or progression.

@gamaryanne
@peterello
The only people who should be paying attention to CA19-9 numbers are the oncologists and physicians monitoring the patient. By itself, the number is essentially meaningless, and it is basically impossible to know if an elevated number is worrisome or decreased number is beneficial.

It reflects some type of inflammation in either bile ducts, kidney, liver, pancreas, stomach, etc and related organs. Or maybe it doesn't and only reflects natural variability of an individual's metabolism.

It is commonly found associated with cancerous tumors, but not always, and one can have cancerous tumors with not much movement in the number.

That is why it isn't used as a test for anything and instead monitored for overall trend over a medium to long term basis so that it can give of clue of changes that should be checked because there might be a problem. A big drop or spike would be concerning because any dramatic changes in metabolism should be evaluated. And investigation might reveal a onetime spike/drop as a momentary blip with no effect on anything.

For someone where an elevated number coexists with cancer, and where it began to fall during ongoing treatments, a continuing downward trends may be good in terms of cancer recovery -- but maybe not. With someone who has cancer but a relatively "normal range" number, a continuing stable range may mean recovery or deterioration. Large drops or spikes are unusual and signal additional investigation.

For most people it is counterproductive to pay attention to CA19-9 numbers unless you are a medical practitioner in control of other testing for yourself.

Don't fixate and stress over something that is meaningless when looked at in isolation from other metabolic functions and current scan results. Pay more attention to things like white and red blood counts for immune system and anemia heath, and items such as bilirubin, which has a more direct correspondence to bile and liver function.

Since a person can not directly influence these factors, the more productive use of time and emotional energy would be to focus on those physical activities and nutritional goals one can do to improve while having the medical team tell you the general trend of your recovery (improving, deteriorating, or staying the same). Hope this helps.