Same problem with chemo and radiation. A tumor may start off with a single cancerous mutation, but by the time it spreads there may be several. Once the cell repair machinery has been broken, the cancer cells are prone for more mutations.
Chemo, radiation, and CRISPR will kill everything it can reach that is susceptible. That leaves everything that was unreachable or resistant behind to start growing again.
Kill cancer cells is easy. Killing ONLY cancer cells is very hard.
alt Hacker News
Same problem with chemo and radiation. A tumor may start off with a single cancerous mutation, but by the time it spreads there may be several. Once the cell repair machinery has been broken, the cancer cells are prone for more mutations.
Chemo, radiation, and CRISPR will kill everything it can reach that is susceptible. That leaves everything that was unreachable or resistant behind to start growing again.
Kill cancer cells is easy. Killing ONLY cancer cells is very hard.