Neratinib in Treating Older Patients With Stage IV HER2-Positive Breast Cancer

PRIMARY OBJECTIVES: I. To estimate the safety and tolerability of neratinib in adults age 60 or older with locally advanced or metastatic HER2 over-expressing breast cancer. SECONDARY OBJECTIVES: I. To describe the full toxicity profile including all grade toxicities measured by National Cancer Institute (NCI) Common Terminology Criteria for Adverse Events (CTCAE) version (v)4.0. II. To estimate the rate of all grades of gastrointestinal (GI) toxicities such as diarrhea, nausea, and vomiting. III. To estimate the rate of dose reduction, delays and discontinuation related to study drug. IV. To describe pharmacokinetic parameters of neratinib in adults 60 and older. V. To estimate overall response rate (ORR) and clinical benefit rate (CBR) defined by Response Evaluation Criteria in Solid Tumors (RECIST) 1.1. VI. To estimate event free survival (EFS), progression-free survival (PFS) and overall survival (OS). VII. To evaluate the role of cancer-specific geriatric assessment tool in predicting treatment toxicities. VIII. To estimate adherence rate to neratinib in older adults (percentage of doses of neratinib taken). IX. To explore the association of pharmacokinetic (PK) parameters and geriatric assessment findings. X. To explore if serum biomarkers of aging (interleukin \[IL\]-6, C-reactive protein \[CRP\], and D-dimer) are associated with treatment toxicities. OUTLINE: Patients receive neratinib orally (PO) once daily (QD) on days 1-28. Cycles repeat every 28 days in the absence of disease progression or unacceptable toxicity. After completion of study treatment, patients are followed up for 30 days and then periodically thereafter.