The purpose of this study is to find out how much lapatinib can enter both normal brains and brains in which tumours secondary to breast cancer have developed.

Lapatinib is an anti-cancer drug taken by mouth which inhibits the HER2 protein, overexpressed in some breast tumours. It is not known whether lapatinib passes through the blood-brain barrier, and, therefore, whether it can target secondary tumours in the brain. This study will investigate whether lapatinib does indeed enter the brain.

Subjects with HER2-overexpressing breast cancer, with and without brain metastases, will receive lapatinib tablets daily for 8 days. The subjects will also receive lapatinib with a small amount of radioactivity attached on the first and last days of dosing to investigate whether it is taken up by the brain, using positron emission tomography (PET) scans.

Inclusion Criteria:

• Female, aged >/= 18 years old
• Advanced or metastatic breast cancer with overexpression of HER2
• Be able to provide written informed consent and comply with protocol requirements
• If of child-bearing potential, using adequate and medically acceptable contraception method
• Have an ECOG performance status of 0-2 and be in stable condition
• Able to lie still on the PET scanner for approx. 1.5-2 h
• Adequate hepatic and renal function
• Patent ulnar artery or collateral arterial blood vessels
• If have CNS metastases, disease must be stable
• Subjects with CNS metastases should have at least a single 1 cm diameter lesion as shown on contrast MRI

Exclusion Criteria:

• Subjects with brain metastases who have undergone prior CNS surgery
• Significant brain abnormalities, neurological disorder, psychiatric disorder or previous brain damage
• Diabetes type I
• History of HIV, hepatitis B or hepatitis C infection
• Current alcohol and/or drug abuse
• Positive pregnancy test or lactation
• Malabsorption syndrome or disease affecting gastrointestinal function that may affect intestinal absorption
• Requirement for additional concurrent anti-cancer therapy
• History of uncontrolled or symptomatic angina
• Concurrent treatment with an investigational agent or anti-cytotoxic therapy or use within 30 days or 5 half-lives
• Known hypersensitivity reaction of idiosyncrasy to drugs chemically related to lapatinib or its excipients
• Concurrent treatment with CYP3A4 inducers and inhibitors
• Unwillingness to refrain from consuming red wine, Seville oranges, grapefruit, pomelo, grapefruit hybrids and their juices from 7 days before Day 1 until collection of the final pharmacokinetic sample
• Known history of claustrophobia
• Known contraindications or likely risk of toxicity to gadlinium-based MRI contrast media
• Presence of cardiac pacemaker, other electronic device or ferromagnetic metal foreign bodies
• Any abnormality found on the MRI scan which, in the opinion of the investigator, may influence the outcome of the PET scans or affect the safety of the volunteer
• Acute or active hepatic or biliary disease
• Any medical condition or circumstance making the volunteer unsuitable for participation in the study.