The case that you present is a very difficult case to treat without a second or third generation TKI. First, if possible, I would suggest to perform the search for mutations on the materials obtained during the biopsy, just to know if there are mutations. This would be very relevant in case of the availability of a second or third generation TKIs, in order to decide which would be the best TKI to be used in association with cycles of chemo (AML like regimens as FLAG-Ida or similar). It is of course less relevant and almost redundant if you cannot use TKIs other than imatinib (that in this case should not be used as the blast clone has been proven to be resistant to it). In the latter case ( lack of a second or third generation TKI) I would add 2 or 3 cycles of chemo to radiotherapy- Then the patient theoretically should be moved to allo Stem Cell Transplant (even haplo if a full compatible sibling or MUD donor cannot be found), after having achieved at least haematological remission. However, if this approach cannot be performed, the only option remains chemo as I do not think that local radiotherapy could be enough to overcome the blastic clone, even if at the moment the bone marrow does not seem involved.
I hope to have understood well the situation of this patient and I remain at your disposition for further problems. Yours, Beppe