Inclusion Criteria:

- Histologically confirmed persistent or recurrent ovarian epithelial or primary
peritoneal cancer

- Measurable disease

- At least 1 unidimensionally measurable lesion ≥ 20 mm by conventional techniques
OR ≥ 10 mm by spiral CT scan

- Presence of ≥ 1 target lesion

- Tumors within a previously irradiated field are not considered target
lesions unless evidence of progression is documented or proven by biopsy 3
months after completion of radiotherapy

- Disease progression during OR persistent disease after 1 prior platinum-based
chemotherapy regimen* for primary disease containing carboplatin, cisplatin, or
another organoplatinum compound

- Initial treatment may have included high-dose therapy, consolidation therapy,
or extended therapy administered after surgical or non-surgical assessment

- Treatment-free interval after platinum-based chemotherapy < 12 months

- Tumor accessible by guided core needle or fine needle biopsy

- Ineligible for any higher priority Gynecologic Oncology Group protocols (i.e., any
active phase III protocol for the same patient population)

- Performance status - GOG 0-2 (patients who have received 1 prior treatment regimen)

- Performance status - GOG 0-1 (patients who have received 2 prior treatment regimens)

- Absolute neutrophil count ≥ 1,500/mm^3

- Platelet count ≥ 100,000/mm^3

- Bilirubin ≤ 1.5 times upper limit of normal (ULN)

- SGOT ≤ 2.5 times ULN

- Alkaline phosphatase ≤ 2.5 times ULN

- Creatinine ≤ 1.5 times ULN

- Ejection fraction normal by echocardiogram or MUGA

- No GI disease resulting in an inability 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)

- Not pregnant or nursing

- Negative pregnancy test

- Fertile patients must use effective contraception during and for ≥ 1 month after
completion of study treatment

- No active infection requiring antibiotics

- No sensory or motor neuropathy > grade 1

- No other invasive malignancy within the past 5 years except nonmelanoma skin cancer

- No history of allergic reaction attributed to compounds of similar chemical or
biological composition to lapatinib

- At least 4 weeks since prior immunologic agents for the malignancy

- No prior trastuzumab (Herceptin®)or cetuximab

- See Disease Characteristics

- Recovered from prior chemotherapy

- At least 6 weeks since prior nitrosoureas or mitomycin for the malignancy

- No prior non-cytotoxic chemotherapy for recurrent or persistent disease

- At least 2 weeks since prior and no concurrent dexamethasone or dexamethasone
equivalent dose > 1.5 mg/day

- At least 1 week since prior hormonal therapy for the malignancy

- Concurrent hormone replacement therapy allowed

- See Disease Characteristics

- Recovered from prior radiotherapy

- No prior radiotherapy to > 25% of marrow-bearing areas

- See Disease Characteristics

- Recovered from prior surgery

- No prior surgical procedure affecting gastrointestinal (GI) absorption

- At least 4 weeks since other prior therapy for the malignancy

- At least 6 months since prior and no concurrent amiodarone

- At least 1 week since other prior and no concurrent CYP3A4 inhibitors

- At least 2 weeks since prior and no concurrent CYP3A4 inducers

- At least 1 week since prior and no concurrent H2 inhibitors or proton pump inhibitors

- Concurrent antacids allowed provided they are not administered within 1 hour
before and 1 hour after study drug administration

- No prior cancer treatment that would preclude study treatment

- No prior lapatinib

- No other prior target-specific therapy directed to the HER family (e.g., gefitinib or
erlotinib)

- No concurrent herbal medications

- No concurrent combination antiretroviral therapy for HIV-positive patients