Statement: Men with Left ventricular ejection fraction > 50% are excluded from participating in the primary trial.
Primary_evidence: DISEASE CHARACTERISTICS:   Histologically confirmed breast cancer   Clinical stage I-III disease   Measurable disease defined as  1 unidimensionally measurable lesion  20 mm by conventional techniques OR  10 mm with spiral CT scan   HER2/neu 3+ by immunohistochemistry or positive by fluorescent in situ hybridization   No known brain metastases   Hormone receptor status unspecified   PATIENT CHARACTERISTICS:   Menopausal status not specified   Male or female   Life expectancy > 12 weeks   ECOG performance status (PS) 0-1 OR Karnofsky PS 80-100%   WBC  3,000/mm^3   Absolute neutrophil count  1,500 mm^3   Platelet count  100,000/mm^3   Total bilirubin normal   AST and ALT  2.5 times upper limit of normal   Creatinine normal OR creatinine clearance  60 mL/min   LVEF  50% as measured by echocardiogram or MUGA scan   No other malignancy within the past year   Not pregnant or nursing   Negative pregnancy test   Fertile patients must use effective contraception   Able to swallow and retain oral medication   No history of allergic reactions attributed to compounds of similar chemical or biologic composition to lapatinib   No ongoing or active infection   No symptomatic congestive heart failure   No unstable angina pectoris   No cardiac arrhythmia   No psychiatric illness or social situation that would preclude study compliance   No other uncontrolled illness   No gastrointestinal (GI) tract disease that would preclude ability to take oral medication   No malabsorption syndrome   No requirement for IV alimentation   No uncontrolled inflammatory GI disease (e.g., Crohn's disease or ulcerative colitis)   PRIOR CONCURRENT THERAPY:   No prior chemotherapy, immunotherapy, radiotherapy, or hormonal therapy for breast cancer   No prior treatment with epidermal growth factor receptor targeting therapies   No prior surgical procedures affecting absorption   No prior surgery for breast cancer   At least 14 days since prior and no concurrent CYP3A4 inducers, including any of the following:   Dexamethasone or dexamethasone equivalent dose  1.5 mg/day, including any of the following:   Cortisone ( 50 mg/day)   Hydrocortisone ( 40 mg/day)   Prednisone ( 10 mg/day)   Methylprednisolone ( 8 mg/day)   Phenytoin   Carbamazepine   Phenobarbital   Efavirenz   Nevirapine   Rifampin   Rifabutin   Rifapentine   Hypericum perforatum (St. John's wort)   Modafinil   At least 7 days since prior and no concurrent CYP3A4 inhibitors, including any of the following:   Clarithromycin   Erythromycin   Troleandomycin   Delavirdine   Ritonavir   Indinavir   Saquinavir   Nelfinavir   Amprenavir   Lopinavir   Itraconazole   Ketoconazole   Voriconazole   Fluconazole (doses up to 150 mg/day are permitted)   Nefazodone   Fluvoxamine   Verapamil   Diltiazem   Cimetidine   Aprepitant   Grapefruit or its juice   At least 6 months since prior and no concurrent amiodarone   At least 2 days since prior and no concurrent gastric pH modifiers*, including any of the following:   Cimetidine   Ranitidine   Nizatidine   Famotidine   Omeprazole   Esomeprazole   Rabeprazole   Pantoprazole   Lansoprazole   NOTE: *Antacids are allowed within 1 hour before and after administration of study drug   No other concurrent investigational agents   No other concurrent anticancer therapy, including chemotherapy, radiotherapy, immunotherapy, or antitumor hormonal therapy   No concurrent herbal (alternative) medicines   No concurrent combination antiretroviral therapy for HIV-positive patients   Concurrent bisphosphonates allowed