Hi,
I am a stage 1b pancan patient. I had a distal pancreatectomy because of concerning cyst, and cancer found after resection. I have had 9 rounds of Folferinox and no CA-19 tests since post surgery, back in August. My case is different than your husband, but my doctor doesn't seem to think the CA test can provide 100% reliable info in mid-treatment, as I asked him once. I was on three chemo agents, but the Oxaliplatin was dropped, due to continuing neuropathy. Every case is different, even with some similarities. I don't know if any of my experience is helpful, but I think it's good to get second opinions from other docs. Best wishes.