Molecular monitoring 101: helping your patients with chronic myeloid leukemia to understand the meaning of molecular response.

For patients with chronic myeloid leukemia (CML), measurement of molecular response (i.e. the level of BCR-ABL1 transcripts) is firmly established as a key element of disease monitoring. Assessment of BCR-ABL1 levels may help to identify early signs of resistance to treatment and enable a timely switch to alternative therapies. Hence, regular and accurate monitoring of BCR-ABL1 transcripts helps to maximize the chance of successful outcomes in CML. Because the incidence of CML is relatively low, many community oncologists encounter only a limited number of cases; measuring and interpreting BCR-ABL1 measurements in a clinically relevant fashion may be challenging. The team at our institution often encounters questions regarding real-time quantitative polymerase chain reaction assessments of BCR-ABL1 levels, International Scale standardization, the implications of achieving or losing molecular responses and mutation monitoring. The aim of this article is to provide practical advice for effective long-term monitoring of patients with CML by addressing frequently asked questions and common case scenarios using guideline- and evidence-based approaches.