I'm so sorry to hear about your dog. My beagle has a growth and they say it's just fatty tissue. My brothers labs both got biopsies and two of his labs died within months of each other. He told me that they were perfectly fine until the day he got the biopsy and they decided to do medical intervention. He said it was awful and he would never put another dog through that ever again. Both of the dogs were siblings too and his wife was horrified to the point they won't get another dog.
My beagle is really healthy and if she started getting sick of course I'd be knocking down the vets door. She gets her checkups and the vet agrees with my stance about medical intervention such as chemo. He actually tries to use less invasive measures because he too believes in quality of life vs quantity.
I look at quality of life vs quantity. I would rather my dog live its last days happy than have my dog suffer for years or months.
It's truly up to the owner what they would like to do with their dog or animal, but I have my strong beliefs on what I would and have done in those situations.

big hugs! You're an amazing animal owner!