Question about long term prognosis with my dogs lipoma?

I was hoping I could find someone who has maybe been through or had some experience with what is going on with our dog, Jamie right now. She is an 8 and a half year old spayed female boxer pitbull cross. We have had her since she was a tiny little 6 week old and she lives indoors with us all the time. Last February she rather suddenly developed a lump on the left side of her neck about the size of a grapefruit. We of course rushed her to the vet, where surgery was performed, test were done and it was determined to be a benign lipoma. Unfortunately, even though it was benign Jamie's tumor was very invasive, involving her shoulder muscle, joint and vessels, so could not be entirely removed. After about 4 months post op it started growing back. We have just been watching her and getting regular checkups to monitor its progress. It is now 1 year since her surgery and the tumor is completely grown back and seems to slowly be getting bigger. We worry BC it is in her neck area and could potentially cause her problems breathing and eating. At least it does not cause her any pain, but I have noticed her swallowing a lot lately and kind of kind of cough/gagging. Not a lot, but a few times over the past couple of months. The vet has been reluctant to perform surgery again, since she will not be able to remove it all and it will most likely come back again. Plus Jamie had a pretty rough recovery from the first surgery. I am mostly wondering if anyone else has experienced this and what options our Jamie girl may have for the future. I would love to hear other peoples experiences and maybe help us make the best decisions for our girl. Thanks