Comment by jobs_throwaway

If we were able to find cancer cells with a precision down to 1 cell, killing them would be trivial. There are lots of cells in a person. It's possible we will get there someday. I think bioengineering is the most likely route. I.e., design a virus to specifically target the type of cancer cell you mean to eradicate.

We already have these nanobots in our bodies. This is the entire rub with cancer. There is amazingly strong selective pressure to evolve ways to hide from our existing nanobots and make them think these are valid healthy cells. Artificial nanobots would be no different in this respect. As for why our nanobots aren't already perfect, it's hard to get perfect. In fact it can go the wrong way, some people's nanobots end up too aggressive and start attacking their healthy cells (autoimmune disorders).

Strictly speaking, no impossible from our understanding of physics, but also an enormous scientific and engineering problem. research into that would take away from people working on more reasonable approaches today.

No. It's hard to get even small molecules where we want them in the body, there's no way that the gigantic molecular clusters called "nanobots" could reliably get access to every single cell. (What may be possible is using things like the Moderna cancer vaccine to make your body an inhospitable environment for the growth and multiplication of the cancer cells.)