Chemo appears to be working

My husband had ca19-9 at 100+ when diagnosed, then was up to 700 when started chemo. Back down to 200 after first round of chemo. He had cisplatin/gemzar first round, and has switched to carboplatin gemzar for 2nd round to avoid nausea. Day 3 and still no nausea, a pretty normal day, too, energy and eating wise. No steroid crash, we asked for a lower dose and only got 6 mg this time. No pain anymore, doctor feels all of these point to a positive reponse. Switched from marinol to megace/megestrol (thank you for all who posted on this wonder drug!), and now he eats like he used to. So, after this round doctor will do some sort of scan to check on tumor (ct probably). Problem is…could only see enlarge lymph nodes on first ct scan, not tumor, stricture in bile duct, or mets in abdomen (he is stage iv extrahep cc). How will doc be able to see progress without spyglass in duct or another lap surgery? Is this a typical respnse to first round of chemo? We are feeling so optimistic!