Yes, the way CRISPR/Cas9 works, the DNA must be damaged.
However, chemotherapy is not very selective about which cells it damages. Here, the DNA is much more difficult to damage if it is already missing the exact sequence being targeted for "editing", so the targeted cells will die while the mutants divide to take their place.
If I thought specific somatic mutations were good drug targets for cancer, I would be more enthusiastic about CRISPR/Cas9 as a less toxic chemotherapy than a gene-editing therapy.
However, chemotherapy is not very selective about which cells it damages. Here, the DNA is much more difficult to damage if it is already missing the exact sequence being targeted for "editing", so the targeted cells will die while the mutants divide to take their place.
If I thought specific somatic mutations were good drug targets for cancer, I would be more enthusiastic about CRISPR/Cas9 as a less toxic chemotherapy than a gene-editing therapy.