Brittany Maynard's decision: a medical perspective

Brittany Maynard was diagnosed with the most aggressive and most common form of primary brain cancer. She thinks she may die before the end of the month -- and she seems very sure that she is going to end her life on her terms.

"I look at the Brittany story; again, she's a hero for what she did because she brought this to the national discourse," University of Southern California Norris Westside Cancer Center director Dr. David Agus said on "CBS This Morning."

There are currently only five states that permit aid in dying. In other states, a patient's best chance is for a doctor to alleviate their suffering.

"We can take away pain, we can take away symptoms that you may have, but at the same time, we can't restore dignity," he said.

He also sees her story as a two-fold failure of the medical system.

"One is, we can't treat this horrible cancer," he said. "And the second is, she and most cancer patients don't trust physicians to be able to alleviate most of the symptoms at the end of life and restore dignity."

While Agus said he would do his best to ease Brittany's symptoms if he were to treat her, that's not the only important piece.

"My job is to educate her with the facts, and then she makes the decision based on her value system," he explained. "It's not the role of the physician to tell a patient what to do. It's a partner system based on her value system and what she believes in, she needs to make the right decision for her."

Brittany's choice: 29-year-old reignites debate about aid in dying

Most glioblastoma patients are terminal, but "it's important to note that it's different for everybody depending on where in the brain it happens," Agus said.

As the disease progresses and the tumor enlarges, he said, it ultimately affects the ability to be yourself.

Although Brittany appeared healthy as she shared her story, Agus doesn't foresee a change in her prognosis.

"I think we can be fooled many times," he said. "Cancer patients can pull up the guts to do what she in such a beautiful and heroic fashion did in that interview. But the disease is real."

Her MRI revealed the cancer spread over a large portion of her brain. Agus said it will only grow exponentially.

"The disease certainly will win here," he said. "I don't think that's disputable."