This is Dr. David
I am a radiation oncology cancer doctor.
I am sorry about your sister.
cancer on the surface of the brain is called leptomeningeal spread
this is a difficult situation and would not benefit from focused stereotactic radiosurgery or cyberknife radiation therapy
she needs whole brain radiation therapy down to the C2 cervical spine level along with high doses of dexamethasone steroid therapy
the whole brain radiation can help kill the cancer cells.
the radiation should be daily over 25 days to a total dose of 45Gy and areas of gross disease which can be seen on the MRI scan can be pushed to 50.4Gy.
she also needs a total spine MRI scan to check for drop metastasis to the dura down in her spine.
in some cases, some patients can get intrathecal chemotherapy into the CSF fluid around the brain through an omaya catheter right into the brain.
chemotherapy agents like methotrexate could help fight her brain cancer
let me know if you have questions.