Molecular patterns associated with imatinib dose interruption. Consecutive days of zero dose, amounting to at least 10% of days of a BCR-ABL1 measurement interval, is likely to lead to a BCR-ABL1 increase. The dose interruptions in both examples were evident at the molecular level, but without an increase above 1% IS. The molecular equivalent of Philadelphia chromosome detection is above 1% IS. The BCR-ABL1 doubling time (DT) at the increase demonstrates an inverse relationship with the length of the dose interruption. The interruptions were the decision of each patient and were declared to their clinicians. Recommencing imatinib led to rapid reduction of BCR-ABL1.