Heather Knies was given a death sentence at the age of 24. She battled not one, but two brain tumors -- one of them a grade 4 glioblastoma, the same kind of cancer that killed Sen. Edward Kennedy in 2010.

But today, six years later, she is cancer-free, and her doctors at the Barrow Neurological Institute in Arizona cannot explain it. Her latest MRI is clean, and she is neurologically intact.

The now-32-year-old Knies has not only outlived her life expectancy, she has married and become a mother. Her successful parenthood is remarkable, as intense radiation and chemotherapy can render cancer patients