Michael Strahan and daughter Isabella reveal her brain tumor diagnosis.
Announcement made on "Good Morning America" with Robin Roberts' interview.
Diagnosed in late October, Isabella underwent emergency surgery and radiation.
Symptoms appeared during her freshman year at the University of Southern California.
Medulloblastoma is a rare brain cancer, most common in ages 5-9.
Isabella underwent surgery on October 27, followed by proton therapy.
Proton therapy completed after a long 30 sessions over six weeks.