My mom was diagnosed with brain cancer, more specifically a high grade glima. she is getting radiation/chemo. should she be waking up with phlegm?

NO: No she should not, she may have respiratory tract infection need to see her doctor possible antibiotics and cough syrup.

No: I am sorry to hear about your mother's diangosis. Phlegm is a rare complaint among high grade glioma patients, though. Most patients with phlegm just have a respiratory tract infection. Dexamethasone (common in glioma patients) can increase susceptibility to upper respiratory tract infections. Keppra (levetiracetam) (also a common medicine in brain tumor patients) can cause coughing. Prayers for your mom...