In early June 2025 I received that same or very similar diagnosis. Mine is stage 4 small-cell esophageal carcinoma. My symptoms were the same as you describe - where I was nearly suddenly unable to keep down even liquids and was living on the tea/Gatorade that did manage to not come immediately back up when I tried to swallow. I lost 45-50 lbs in about a month. My oncologist was hopeful that it would not take more than 'a few days' for the chemo to shrink my tumor enough to begin getting and keeping down food. Based on that, I held off on having a feeding tube surgically installed.

For me, the chemo worked exactly as hoped. My first chemo was on a Friday and I was able to eat a couple of slices of Pizza on Sunday evening. I've now completed chemotherapy and my last scan was clear. I'm continuing on immunotherapy on an indefinite timeframe with the plan of getting CT scans on a ~quarterly basis.

My advice is to discuss everything with his oncologist, but hold on through that first chemo treatment to see how he responds. Note that my cancer was/is small cell, which is highly aggressive but also highly responsive to the chemo.

Hope this helps.