Breast milk paclitaxel excretion following intravenous chemotherapy-a case report

Breast cancer can be diagnosed during pregnancy and in the peri-partum period, and the potential exposure of a foetus or neonate to chemotherapy is of concern to mothers and clinicians. Paclitaxel is a commonly used agent in breast cancer, but little is known about its excretion in breast milk. Breastfeeding during chemotherapy has been traditionally cautioned against due to the risk of neonatal exposure to chemotherapy agents, however, data are limited. We measured serum and breast milk concentrations of paclitaxel in a 33-year-old woman with an early breast cancer diagnosed during pregnancy and treated with weekly paclitaxel 80 mg/m². We found breast milk paclitaxel levels drop below the minimum quantifiable dose at 72 h following chemotherapy, with a relative infant dose of 0.091%. Breast milk excretion of paclitaxel following a dose of 80 mg/m² is negligible at 72 h, and this may be a safe time to recommence breastfeeding following exposure.