I like the information provided by the website Lab Tests Online (https://labtestsonline.org/) by the American Association for Clinical Chemistry (AACC). The information is trustworthy and easy to understand.

Here's the page about Cancer Antigen 19-9 (CA 19-9) https://labtestsonline.org/tests/cancer-antigen-19-9
CA 19-9 is primarily used to monitor response to pancreatic cancer treatment and to watch for recurrence. In the section called "What does the test result mean?" it states:
"Levels of CA 19-9 that are initially high and then fall over time may indicate that the treatment is working and/or that the cancer was removed successfully during surgery. Levels that remain high or rise over time may indicate that treatment is not working and/or that the cancer is recurring."

@lisarlee, I understand that your step daughter may not have complete faith in the CA 19-9 test. It is only one test. But taking a blood sample is a simple, non-invasive test to keep check on things. Your cancer team will use multiple tests in addition to the CA 19-9 test to monitor the cancer, how the treatment is working or not, and watch for signs of recurrence.

For the moment, I think both you and @colorafo19 can accept the lower numbers as good news and have confidence in the teams monitor of the cancer. What other tests have you had? How are you feeling?

It’s very good news, you want to see the number trending down. My husbands CA19-9 is very indicative of how the chemo is working.