That’s a cool question! I had to read a bit about it because it’s not my topic. Apparently nanobots have been approved to treat a cancer patient as a clinical trial. I find that amazing!
So they have been design in a way that they can transport a cancer drug through the blood and ignore healthy cells. When the nanobot finds a cancer cell it “opens up” and gets the drug to the cancer cell, killing it. How.cool.is.that?