Given that the fusion protein is usually characterized by chromosomal translocation, such abnormalities represent a huge restructuring of genomic material, and would not be a good target for a precision tool like CRISPR-Cas9. You could theoretically use something like CRISPR-Cas3 to shred the extraneous material, but to what end? I would think that such a cell is not worth repairing and should instead be targeted for destruction through other therapies.