In February of this year I stopped taking Sprycel (20mg) in order to test low residual durability.
My PCR was below quantification (i.e. < 0.01%), but still considered detectable. Some reports gave Undetected, some gave <0.01% (M.D. Anderson does not report more than two decimal places).
Over nine months, my PCR remained the same for the first several months but then started to show up and down PCR's. The last one before I restarted approached MMR (one log increase). I decided to resume Sprycel at that time (very low dose) to test if my PCR would fall back. I am pleased to report that my PCR has indeed fallen back to barely detectable (<0.01%) agaom. It took nine months for my PCR to rise and only two months on the same dose to drop it back.
As important, my bone marrow shows normal trilineage hematopoiesis (blood making) and no signs of CML (but with depressed red cell formation (Sprycel gives me mild anemia even at 20mg) and no blasts.
The good news is that stopping and re-starting Sprycel, in my case, was no big deal. I will try cessation again - and again and again until it sticks (I believe that Leukemic stem cells burn out over time). I will wait, however, until I am "undetected" for a period of time before trying again. Or I might go one month on - one month off.
Trey: I don't know about the Trisomy 8 yet. Cytogenetics is pending.