Can your ca19-9 level go up even though tumors are shrinking?

Ruecatt

My husbands, who has metastatic pancreatic cancer (spread to his liver) latest Ct scan showed that his tumors have slightly shrunk. The tumor on the pancreas from 3.7cm to 3.0cm and the liver tumors have also shrunk some. However his CA19-9 level has gone up. He has had 4 rounds of chemo so far. Does that mean his treatment is not working? His CA19-9 level has been normal but has increased, started at 9 → 14 → now 38 (which is considered high).