Pancreatic cancer with liver metas and cough

Diagnosed 16 months ago with adenocarcinoma of pancreas with liver metas, symptoms driving me to Dr were weight loss and severe cough. (CT of chest found liver mass). 9 months of chemo stopped the cough, and shrunk the tumors, stopped because of severe neuropathy, tumors grew, had nanoknife procedure, liver tumors grew, started new chemo without effect and Cough is back! Severe, debilitating, dry cough. Can't find the source. Put on steroid and started KRAS inhibitors. Tumors have stopped growing, labs and weight are good. But the cough is relentless. Anyone else have a cough like this? My Dr says he has not known of cough with pancreatic cancer and the tumor doesn't push on diaphragm. GI says reflux wouldn't cause a cough like this. Lung evaluations are good. Please share if you have any advice. Thanks.