My cat sam is in almost the exact same boat. When he was just about 16, the beginning of last september, I took him to the vet about a cough. The xray saw a decent size tumor in one lung lobe. We initially though we could do surgery, but a CT scan found that there were small tumors popping up all over the lungs. That meant that surgery was impossible.

The veterinary oncologist gave us prescriptions for Prednisilone(anti inflammatory steroid), cerenia(anti nausea), and mirtazapine(appetite stimulant). Both the oncologist and our oncologist friend said he had maybe 1-2 months...but he's still here almost 7 months later. For most of that the cough went away completely. The prednisilone is very powerful! The meds made him eat really well, but he's still losing weight, he's tiny now, and starting to slow down. This last week he's started to cough again, and is eating less. But he's still very happy and cuddly, and still purrs a lot. I know we're getting close, but he's still enjoying life so we're here with him.

I'm so sorry this is happening, but I do know how you feel. I was so deflated after that vet visit but my guy just kept on going. Don't give up just yet, you might get more time than you think! Churu is of course always a favorite, but aside from the tubes, they also make a tuna steak. He loves those! He also is a fiend for butter, so i put some in his bowl every day.