Patients with CML ≥60 years were given 200 mg of bosutinib for 2 weeks before increasing the dosage to 300 mg. In the absence of meaningful toxicity, patients with BCR::ABL1 transcript at 1% or lower stayed on 300 mg, while patients with transcript > 1% increased to 400 mg. This evidence concerns the gene BCR and chronic myelogenous leukemia, BCR-ABL1 positive.