Breastfeeding in patients with chronic myeloid leukaemia: case series with measurements of drug concentrations in maternal milk and review of literature

Breastfeeding in patients with chronic myeloid leukaemia (CML) who take tyrosine kinase inhibitors (TKIs) is not recommended but interruption of TKI treatment may cause the loss of remission. We observed the kinetics of the leukaemic clone in 3 women with CML in accordance with treatment interruptions for pregnancy and breastfeeding. The concentrations of nilotinib and imatinib in maternal milk were measured when the breastfeeding period was over. Nilotinib transfer into human breast milk was demonstrated for the first time and had a maximum concentration (Cmax) 129 ng/ml after 4 hours of the drug intake at a dose of 400 mg. The Cmax of imatinib in maternal milk ranged from 420 to 1411 ng/ml after 4-8 hours of the drug intake at a dose of 400-600 mg. Breastfeeding without TKI treatment may be safe with molecular monitoring, but preferably in those patients with CML who have durable deep molecular response.