RE:Edited cells might cause cancerBut others have doubts about these studies.
https://seekingalpha.com/article/4181056-crispr-therapeutics-cancer-concerns-unjustified-market-reaction
"[...]there are two broad approaches to gene editing - one, replacing a mutated gene, and two, disrupting a mutated gene so it doesn't express a harmful protein. The second is also called gene knock down. Gene disruption, which is the approach taken by "CRISPR Therapeutics' sickle-cell and thalassemia programs as well as Editas Medicine's lead product, targeting a form of blindness, and others in its pipeline," can occur even when p53 is activated. Meaning, this approach does not cause cancer. The same goes for NTLA's transthyretin amyloidosis.
The problem only occurs in what is called double stranded breaks or DSBs; that is, when CRISPR tries to replace mutated DNA with healthy DNA. That seems to make p53 go haywire."
So, it seems to be hard to replace a gene vs disrupting it. But I don't understand what you can do by disrupting a gene. It's way over my head. I think in some disease, just disabling a gene would cure the disease but it will not work if the good version of the gene is needed.
Disrupting a gene could be a good possibility to treat cancer (we are far from this) by knocking down the bad gene mutation that causing cells multiplication.