ELBA: Exemestane and Lapatinib in Advanced Breast Cancer

Inclusion Criteria: * Histological diagnosis of breast cancer * Indication for hormonal therapy (ER and/or PgR positive) * Stage IV disease * Female gender * Postmenopausal status (patients treated with LHRH analogs are eligible for the Phase II part of the study) * At least one target or non-target lesion according to RECIST criteria * ECOG Performance Status 0-2 * Adequate bone marrow (neutrophils \> or = 1.500/mm³, platelets \> or = 100.000/mm³ and hemoglobin \> or = 9 g/dl), hepatic (GOT, GPT \< 2.5 e bilirubin \<1.25 times the value of upper normal limit) and renal (creatinine \< 1.25 times the value of upper normal limit) function * Adequate cardiac function (FEVS \> or = 50%) * Able to take oral medications * Life expectancy \> 3 months * Signed informed consent Exclusion Criteria: * Any previous hormone therapy for metastatic disease * More than one line of chemotherapy for metastatic disease (first line chemotherapy is permitted) * Symptomatic cerebral metastases * Planned concomitant radiation therapy in the first month of therapy (for those patients participating in the dose finding phase of the study) * Previous therapy with exemestane, including as adjuvant therapy (previous therapy with non-steroidal aromatase inhibitors is permitted) * Previous or concurrent malignancy in past 5 years (excluding adequately treated basal cel or spinocellular skin cancer and in situ carcinoma of the cervix) * Treatment with experimental pharmacologic therapy within 4 weeks of enrollment in the study * Unable or unwilling to provide signed informed consent * Any concurrent illness that would, in the Investigator's opinion, contraindicate the use of the study drugs. * Active infection * Assumption of CYP3A4 inhibitors or inducers (ketoconazole, itraconazole, fluconazole, macrolide antibiotics, antidepressives, calcium-antagonists, cimetidine, carbamazepine, phenytoin, barbiturates, rifampicin e glucocorticoids) * Pregnancy or lactation * Unable to comply with follow-up * Active hepatobiliary disease (with the exception of Gilbert's syndrome, asymptomatic biliary calculi, hepatic metastases or stabile chronic hepatopathy)