Intrathecal administration of pertuzumab and trastuzumab will occur via lumbar puncture (spinal tap) under fluoroscopic guidance by interventional radiology at Duke University Medical Center. The spinal needle will be inserted into the spinal column and 7 mL of cerebrospinal fluid (CSF) will be collected. Once the CSF is removed, the intrathecal pertuzumab and trastuzumab will be administered using aseptic technique. At certain time points the CSF will be analyzed for free cell DNA. If subjects consent, the CSF fluid will also be stored for additional future research.