I know how you feel, cancer is a battle you can't win. No matter what you do cancer winds out in the end. Several years ago I took in a rescue shepherd, she had been badly abused before I got her. I had her for less than five years, took her to the vet just for a regular checkup, she had lymphoma. I to did not do chemo, took her home to care for her and said when she got sick I'd bring her back. 5 weeks to the day she was diagnosed I had to put her down. Got up that morning and she was all bloated and having a hard time to breathe. I brought her in and they told me she may live another day or two. I didn't want her to suffer not being able to breathe and strangling by the lumps in her throat. I had promised her my face was the last thing she'd see and I kept my promise to her, she died peacefully in my arms.
I was the only human that ever showed this dog any love or attention and she bonded very closely and very quickly and I felt this dog never caught a break but at least she had five years with me where she got to live a decent life. She had been kept in a crate for 18 months because the husband kept her only so the x wife couldn't take her. What kind of a jerk abuses an animal just to get back at his x wife?
He is your friend, your partner, your defender, your dog. You are his life, his love, his leader. He will be yours, faithful and true, to the last beat of his heart. You owe it to him to be worthy of such devotion"