u/Careless-Catch331

My dad has been off chemo for over a month. Since dx in Jan 2024, prior treatments include surgery, mFolfirinox, RMC-6236, Gem/Abx, mFolirinox - all of which failed. His tumors grew. He had a CA 19-9 done around end of March/early April - it was 4900. End of April after stopping treatment, another test was run by a different hospital (MSK) and the level was 2900. Massive 2K drop. Not sure how to interpret this? I know the test is not a tumor marker, but this seems pretty remarkable?