Abstract
BackgroundBrain metastases are common in human epidermal growth factor receptor (Her)-2-positive breast cancer. Drug access to brain metastases and normal brain is key to management of cranial disease. In this study, positron emission tomography (PET) scanning after administration of radiolabelled lapatinib was used to obtain direct evidence of cranial drug access.MethodsPatients with Her-2+ metastatic breast cancer either with at least one 1-cm diameter brain metastasis or without brain metastases underwent dynamic carbon-11 radiolabelled lapatinib ([11C]lapatinib)-PET. Less than 20 μg of [11C]lapatinib was administered before and after 8 days of oral lapatinib (1,500 mg once daily). Radial arterial blood sampling was performed throughout the 90-min scan. The contribution of blood volume activity to the tissue signal was excluded to calculate lapatinib uptake in normal brain and metastases. Partitioning of radioactivity between plasma and tissue (V T) was calculated and the tissue concentration of lapatinib derived. Plasma lapatinib levels were measured and adverse events noted.ResultsSix patients (three with brain metastases) were recruited. About 80% plasma radioactivity corresponded to intact [11C]lapatinib after 60 min. PET signal in the brain corresponded to circulating radioactivity levels, with no [11C]lapatinib uptake observed in normal brain tissue. In contrast, radioactivity uptake in cranial metastases was significantly higher (p = 0.002) than that could be accounted by circulating radioactivity levels, consistent with [11C]lapatinib uptake in brain metastases. There was no difference in lapatinib uptake between the baseline and day 8 scans, suggesting no effect of increased drug access by inhibition of the drug efflux proteins by therapeutic doses of lapatinib.ConclusionsIncreased lapatinib uptake was observed in brain metastases but not in normal brain.Trial registrationClinicalTrials.gov: NCT01290354
Highlights
Brain metastases are common in human epidermal growth factor receptor (Her)-2-positive breast cancer
In order to evaluate lapatinib access into normal brain and brain metastases, a positron emission tomography (PET) study was performed with carbon-11 radiolabelled lapatinib ([11C]lapatinib) in patients with Her-2-positive breast cancer
PET scanning The scanning procedure was well tolerated by all patients
Summary
Brain metastases are common in human epidermal growth factor receptor (Her)-2-positive breast cancer. Positron emission tomography (PET) scanning after administration of radiolabelled lapatinib was used to obtain direct evidence of cranial drug access. Overexpression of human epidermal growth factor receptor (Her)-2 in breast cancer is considered an independent factor for development of brain metastases [1] with up to 37% of patients with Her-2-positive disease relapsing intracranially despite control of extra-cranial. In order to evaluate lapatinib access into normal brain and brain metastases, a positron emission tomography (PET) study was performed with carbon-11 radiolabelled lapatinib ([11C]lapatinib) in patients with Her-2-positive breast cancer. In order to test our hypothesis that therapeutic doses of lapatinib increase brain access into the brain and brain metastases, by blockage of the drug efflux pump, paired [11C]lapatinib-PET imaging in patients before and after therapeutic doses of lapatinib was performed.
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