The CA19-9 marker tests can be wrong but your wife's markers were low during chemo, and went up after chemo stopped; you rightly noticed. If there is nothing else that could have caused the markers to rise eg an illness or infection with fever, go get it checked properly with a scan. My husband had surgery in Dec 2023 and it was Stg 2b. Surgeon was optimistic he got it all out. A year later my husband is still on Gem-Abraxane because oncologist says with pancreatic cancer, the cancer cells can be floating around somewhere in the body and the Gem-Abraxane can hopefully control it. So go get an oncologist to check it and to order a scan. It could be nothing but getting it checked means you know for sure.