That's doesn't even account for the probably larger number of bugs that develop over the lifetime of the system. Then, once a cancer develops it evolves further mutations over time.

You probably cannot defeat cancer merely by genetic engineering every new birth

Epigenetics is the word you're looking for here. And probably some healthy dose of metabolomics. Cancer is way more complex than "just" changes in the genetic code.

I don't think so. I'm sure there are epigenetic effects in cancer but I'm also pretty sure that cancers develop new mutations as they proceed. Ones that fool the immune system or chemotherapy agents get selected for and drive the cancer forward

You can fix all the bugs in the fifty-year old software project... by writing a new version of it.

Sometimes the right solution doesn't deal with existing problems but tries to go somewhere else entirely.

So you're suggesting they're going to just give birth to a super race of people ?

I'm suggesting we build a new one, either through genetic engineering or replacement of parts. In the context of Zuckerberg and Chan, this would involve promoting the funding and research of things like stem cells, artificial organs, test tube babies, etc. Given how much such things are opposed to the public, a lot of things could come out of it.

That position assumes things about the fundamental nature of cancer that are not at all proven.