Long-term TCR repertoire monitoring may have potential as a biomarker for disease progression. Two patients were followed for 8 years. (A) Patient demonstrates an initial biclonal expansion that became monoclonal and then decreased during hematologic remission after therapy. When the clone re-expanded, remission was maintained with the resumption of therapeutic intervention. (B) Patient with initial biclonal expansion that became monoclonal after treatment entered hematologic remission despite the presence of a clone that dominated the TCR repertoire. Emergence of a new clone (Vβ12) preceded relapse and eventually required further intervention. At the most recent measurement, this clone now accounts for > 80% of CD8 T cells. Amino acid sequences of the expanded T-cell populations are shown next to relevant time points.