Would you start TKI therapy in a patient with new diagnosis of T-ALL without BCR-ABL gene rearrangement on FISH but found to have very low level p190 transcript on RT-PCR?

I would not. I don't necessarily have any evidence to support this, so this is simply an opinion. I have seen this a couple of times in my clinical practice.

If there is truly BCR-ABL present in this patient's leukemia, the level of it would have to be extremely low to only be detectable at this reported level by RT-PCR. From that, one could conclude that only a very small proportion of this patient's T-ALL would likely be susceptible to ABL kinase inhibition. I think it is unlikely then that the patient would derive much benefit from the addition of a TKI, but it could cause toxicity and increase the cost of their care.

More likely, this is probably a false "positive" (if one can call it that). The laboratory that performed the assay may b...