TFR in chronic myeloid leukemia: Lights and shadows. In several studies, NK cell numbers or functional subsets of NK cells were shown to be higher in patients who maintain TFR

'Among challenges of TFR, it is also included the better identification of patients who have a high probability of relapsing compared with those who experience a successful TFR. Some of the most promising data involve the field of immunology, especially T-cell cytotoxicity and NK cell effects. In several studies, NK cell numbers or functional subsets of NK cells were shown to be higher in patients who maintain TFR than in those who lose molecular response during TKI discontinuation.'

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7520857/