Exploratory Lapatinib (Positron Emission Tomography) PET Study in Subjects With Breast Cancer

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.