Lapatinib concentration in cerebrospinal fluid in two patients with HER2-positive metastatic breast cancer and brain metastases

Lapatinib is able to penetrate brain metastases from HER2-positive breast cancer. We assessed lapatinib concentration in cerebrospinal fluid (CSF) of two patients with HER2-positive metastatic breast cancer and brain metastases, and we found low levels of the drug in CSF of both patients. Lapatinib concentration in CSF may not be a reliable surrogate of its distribution in brain metastases.