Bone Cancer

A very good friend of mine just died of bone cancer after just 3 wks of finding out he had it, i'm confused here and need some questions answered, he had back pain so he went to the drs and got pain pills and the dr took an x-ray then sent him home to rest, 3-4 wks later he goes back to the dr with more pain then before, so they take more x-rays and run tests, finding the cancer, they put him thru aggressive chemo, a few dys later he lapsed into a coma for 3 dys, he woke heavyly sedated and died 2 dys later, does that sound the coma was triggered by a reaction to the chemo? did he die of heart failure? why didn't the first x-ray show anything, then 3-4 wks later the other x-rays showed cancer? this cancer went into his spine so does that make it worse and less likey to survive? could he of survived if he had done anything different? help I'm so confused and full of sadness, and nobody to ask these questions to!