One anecdote about experimental cancer treatment: Expect the unexpected.

My mother had uterine cancer. As it progressed, she entered a study and took experimental drugs.

The cancer spread to her spine, which is highly unusual for uterine cancer. Because it's unusual, her oncologist went into denial and didn't treat her appropriately.

I remember listening to the oncologist say "it can't be spinal cancer, that doesn't happen" while I could see that the infectious disease expert was humoring the oncologist and checking my mom for spinal meningitis.