There are quite a few cell therapies that have a very high success rate for stage 4 cancer. Most of them are still in clinical phase, however a couple are approved for commercial use for only specific types of cancer even though they work with all of them. They are all CAR T-cell therapies, or tumor infiltrating lymphocyte therapies.
It’s not a cure but it is quite effective. I make one at work and the only option before was chemo which has a 10% success rate, but our therapy has a 70% success rate. It’s expensive, though.