GW572016 In Patients With ErbB2 Over - Expressing Advanced Or Metastatic Breast Cancer

Inclusion Criteria

A subject will be considered eligible for inclusion in this study only if all of the following criteria apply:

• Life expectancy of ≥16 weeks from the start of lapatinib therapy;
• Signed informed consent obtained from the patient;
• Subjects must have histologically confirmed breast cancer with advanced (Stage IIIb, IIIc with T4 lesion) or metastatic disease (including recurrent patients);
• Subjects must meet the following criteria regarding prior therapy:
• Anthracyclines, taxanes:
• If anthracycline- and taxane-containing regimens are administered sequentially;
• Subjects should have been provided with at least 2 cycles each and at least 4 cycles in total.
• If anthracycline- and taxane-containing regimen are administered concurrently;
• Subjects should have been provided with at least 4 cycles in total. or
• Subjects should have been provided with at least 2 cycles in total and provided progressive disease occurred.
• If anthracycline- and taxane-containing regimen are administered separately;
• Subjects should have been provided with at least 4 cycles each. or
• Subjects should have been provided with at least 2 cycles each and provided progressive disease occurred each regimen.
• Trastuzumab:
• Prior treatment must contain trastuzumab alone or in combination with other chemotherapy for at least 6 weeks of standard doses.
• Subjects must meet the following criteria regarding ErbB2 expression (defined by the following status before undergoing trastuzumab therapy.)

Patients with ErbB2 overexpression:

• 3+ by IHC, or FISH+
• 2+ by IHC and FISH+ are also eligible. However, patients with "2+ by IHC" who have previously been treated with trastuzumab should undergo FISH before study entry, if they have not had this test performed before, and are considered eligible only if their tumours are categorised as FISH+.
• Documentation of tumor progression or relapse after the most recent treatment is required.
• Archived tumor tissue must be available to compare tumor response with intra-tumoral expression levels of biomarkers (ErbB1 and ErbB2).
• Measurable lesion(s) according to RECIST (Response Evaluation Criteria in Solid Tumors); (See "6.3. Efficacy")
• A female, ≥20 and ≤74 years (at the time of giving consent), is eligible to enter and participate in this study if she is of:
• Non-childbearing potential (i.e., women with functioning ovaries who have a current documented tubal ligation or hysterectomy, or women who are post-menopausal, i.e., at least 1 year has past since the last menstrual period); or is
• The subject has a negative serum pregnancy test at screening, and agrees to one of the following from 2 weeks prior to administration of the first dose of lapatinib until 28 days after the final dose of lapatinib＊.
• Complete abstinence from intercourse:
• Consistent and correct use of one of the following acceptable methods of birth control:
• Injectable progestogen;
• Any intrauterine device (IUD);
• Oral contraceptives (either combined or Progestogen only);
• Barrier methods including diaphragm or condom with a spermicide.
• At least 3 weeks since the last dose of prior last chemotherapy, immunotherapy, biologic therapy, hormonal therapy, or radiotherapy (except for local radiation therapy to pain relief) for cancer or since the date of completion of surgery (except for minor surgical procedures) before beginning treatment with lapatinib, except for trastuzumab which must be discontinued at least 2 weeks prior to beginning of study drug. Subjects must have recovered or stabilized sufficiently from side effects associated with prior therapy;
• Prior to enrollment, radiation therapy is allowed to a limited field (e.g. painful bone mets, painful lumps), if it is not the sole site of measurable and/or assessable disease. Patients must have completed treatment and adequately recovered, in particular from bone marrow suppression.
• Subjects who are not on bisphosphonate therapy. Bisphosphonates initiated