Disease	Breast cancer
Stage of Disease/Treatment	Metastatic/advanced
Prior Therapy	No designated number of regimens
Type of Study – 1	Phase II
Type of Study – 2	Single arm
Primary Endpoint	Correlative endpoint
Secondary Endpoint	Safety
Additional Details of Endpoints or Study Design
This was a single‐center, open‐label, and prospective phase II study (NCT03075995). The study involved two clinical states; all patients were required to receive lapatinib plus physician's choice chemotherapy. In the fasted state, all participants took lapatinib (750–1,250 mg a day according to investigator's direction) on an empty stomach for 10 days. In the fed state, all patients were assigned to take lapatinib with breakfast for the next 10 days. The breakfast consisted of one egg, 250 mL whole milk, and 100 g bread or fried rice noodle. Patients were required to write down daily drug intake, food intake, and relative adverse reactions in a diary. Blood samples were collected on days 9, 10, 19, and 20.
Patients with HER2‐positive metastatic breast cancer who planned to take lapatinib for at least 1 month were eligible. All patients were provided a full explanation of the study by the study investigator and signed an informed consent before study procedures.
The primary endpoint was to quantify the impacts of food on the steady‐state plasma concentration of lapatinib in patients with metastatic breast cancer. The secondary endpoint was to identify any safety distinctions between the different modes of lapatinib administration. No patients were allowed to take drugs known to inhibit CYP3A4 enzyme activity during the study.
Toxicities were assessed and graded according to National Cancer Institute Common Terminology Criteria for Adverse Events version 4.0. A sample size of 10 patients provided 90% power for the test on the account of the data from the 27‐patient phase I study mentioned above, using one‐side alpha level of 0.025.
Investigator's Analysis	Active and should be pursued further