a GSD with osetosarcoma

its about a beautiful GSD, male about 8 years old. he is so intelligent but the only problem is that it is having a malignant bony cancer. he cant walk properly and always lifts the hind limb as it is so painful for him. the femur bone lysis has occurred and now it has spread to other limbs also. what a pity. if he takes pain killers drugs , he just vomits blood. so he is on injectables, at least will get some relief from pain. but what is going to happen finally.......... even the owners are prepared for it......how the God can be so cruel to some.......