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?