Please, does anyone have any advice or experience in the past with osteosarcoma in dogs?

My beloved dog Bella has been limping lately. We took her to the vet today and had an x-ray done which revealed a possible Osteosarcoma. He said it was good we caught it this early and that there is a possibility it is a fungus but was 90% sure it was the osteosarcoma. The location is the front Left leg at the shoulder. She is eating and playful and the area is not swollen or appearing ill to the eye. Let me tell you a little about this dog so you can better understand my situation.... I found Bella about a year and a half ago running down the busy road into incoming traffic. I pulled over and coaxed her in my direction which she happily came. She was so friendly and trusting I put her in my car and brought her home. I advertised in the local newspaper and when no one responded i took her to the vet to get checked up. They found heartworms which were treated and a tumor on her left side. It was positive for a mast cell tumor and was treated...(cont. below)