Chronic Myeloid Leukemia: a curable blood cancer?

Patients with Chronic Myeloid Leukemia (CML) used to have only one treatment for a long term survival: allogeneic bone marrow transplantaion.
With the advent of Tyrosin Kinase Inhibitors (TKIs) that revolutionized the CML treatment, majority of CML patients have a life span close to that of general population.
However, due to some reasons, such as cost, side-effects, some patients who have been on TKIs for many years with good response had to stop the TKIs. Surprisingly, in about 1/2 of those patients who stopped the TKIs, disease never recurred. This is called "Treatment-Free Remission (TFR). How long do the CML patients having TFR have to wait before declaration of CML? Only time will tell.