That's not entirely true. It's very effective against blood cancers but less so for solid tumors, where its effect seems to interact strongly with aspects of the tumor microenvironment.
As the father of a kid that died of bone cancer that is par for the course. Other cancers have made HUGE improvements but the hard dense sarcoma tumors still sit in the 1980s in terms survival rates.
I'm very sorry to hear of your loss. I can't begin to imagine.