Help! Should I amputate?

Bentley is a 3 year old pitbull that was just diagnosed with soft tissue sarcoma in his back right leg close to his paw. The vet recommended amputation but I don’t know if that’s the best way to go. He had already had TPLO surgery for his torn acl on the same leg last year. If he looses that leg is the other acl going to tear? He already has a 50% chance of that happening. I’m just afaird to go through with the amputation when there could be another cure to his cancer such as tumor removal and radiation.