Bacteria are rapidly emerging as a new class of "living medicines" used to kill cancer cells. We're still a long way from a "cure" for cancer. But one day we could have programmable, self-navigating bacteria that find tumours, release treatment only where needed, then vanish without a trace. Here's where the science is up to. Current treatments aren't perfect Many tumours are hard to treat. Sometimes, treatments cannot penetrate them. Other times, tumours can "fight back" by suppressing certain