Chronic Myeloid Leukemia Coverage from Every Angle

Case Study in CML: Is Imatinib Treatment Safe During Breastfeeding?

By: Melissa Steele-Ogus
Posted: Wednesday, October 14, 2020

First-line therapy for Philadelphia chromosome–positive chronic myeloid leukemia (CML) includes tyrosine kinase inhibitors like imatinib. Although it is recommended that lactating women receiving imatinib treatment discontinue breastfeeding, Hiroshi Azuma, MD, PhD, of the Asahikawa Medical University in Asahikawa, Japan, reported a case presentation of a young mother whose imatinib use during breastfeeding for the first 5 days appeared to be safe. However, they cautioned, “long-term safety is unknown, and further studies are warranted.” The case report was featured in the Journal of Oncology Pharmacy Practice.

The 32-year-old woman was 13 weeks pregnant when diagnosed with Philadelphia chromosome–positive CML. Interferon-alpha was given and did not cross the placental barrier until the second trimester. At 28 weeks of pregnancy, she was given 400 mg/day of imatinib and achieved hematologic remission. She was admitted to the hospital at 35 weeks due to premature rupture of membranes, and delivery was induced.

The preterm female infant was successfully delivered vaginally but had a low birth weight and an Apgar score of 8 points at 1 minute. Due to the risk of imatinib ingestion from breast milk, clinicians determined that the baby should be fed only by colostrum and formula. She received breast milk for the first 5 days, after which she was switched to formula.

During these first 5 days, the imatinib concentration was measured in maternal blood, breast milk, and infant blood. Clinicians determined the milk/plasma (M/P) ratio to be 0.35; an M/P value of more than 1 indicates it is concentrated in breast milk. Likewise, a relative infant dose (RID) of less than 10% is considered safe; here, the RID of imatinib was calculated to be 1.4%. Furthermore, the infant serum level of imatinib was 27 ng/mL, much lower than the 1,000 ng/mL target trough level.

Disclosure: The study authors reported no conflicts of interest.

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