"I'm done with this," Ryan Kennedy told his mother. After five years of fighting a rare form of brain cancer, with seven surgeries, four rounds of chemotherapy and two bouts of radiation, the 9-year-old from Clarkston, Mich. said he had enough.

In February, Ryan's mother told him about another surgery that doctors said would buy him about three more months, but potentially leave him on a breathing and feeding tube, according to the Oakland Press.

"When I told him about it, he said, 'No. I told you, Mom, I don't want to do anything anymore,'" Kimberly Morris-Karp told the Oakland Press. "He literally screamed and cried in hysterics, saying 'I'm done. I'm done with this.'

"The selfish part of me wanted to say, 'No, I want you to do this,' but I said, 'OK, this is what you want,'" Morris-Karp said. "And we keep asking him over and over again. Once a week, I would ask him the same question: 'Are you sure you're OK with this? You don't want anymore treatment?' 'Yup, I'm sure,'" she said Ryan replied.

The decisions to end treatment for children fighting cancers are especially difficult ones to make, said Dr. Lisa Humphrey, director of the pediatric palliative care program at University Hospitals Rainbow Babies & Children's Hospital in Cleveland, because decisions tend to be based in the instinctual place where parents are never supposed to bury their children, she said.

"For Ryan to have the courage to make such a decision and be able to talk to his family about it speaks volumes about the journey that they went on together," she said. "We know for a fact that children who have life-threatening illnesses mature very quickly in some ways. They're able to understand what is at stake, and they often have an exquisite sense of what's going on in their bodies."

Often times, children with life-threatening illnesses will ask if they're dying, Humphrey said. But, in many cases, they won't ask their parents. Instead, they'll ask an aunt, a family friend or a nurse.

"They know what's going on with their bodies and they're curious and want to check in, but in a way, the child wants to protect the parent a much as a parent wants to protect their child,"  Humphrey said.

It's best for parents to be open and act as a sounding board for their child and gauge how much they understand about their illness and potential prognosis, she said.

Each year, about 50,000 children in the United States die from life-threatening illnesses. A 2004 Swedish study found that, out of 300 families who had children who died from terminal illness, about 35 percent of them discussed the pending deaths with them. The survey showed not one family regretted it. Of those who did not discuss death with their children, 27 percent of the families reportedly regretted their decision.

Ryan recently became a trending topic on Twitter when it was thought to be his dying wish. Celebrities, including Britney Spears, offered their support for the child.

"There's this sweet boy who is battling cancer, and his biggest wish is to trend on Twitter. Let's make it happen! #ryankennedy," Spears tweeted on May 6.

'Ryan really wasn't the one who wanted to trend on Twitter - he's 9 - he doesn't have a Twitter account," Morris-Karp told CNN. "He really didn't even know what Twitter was."

Twitter wish or no wish, the word has gotten out on Ryan's cancer fight. And the trending topic also happens to coincide with the month of May,  National Brain Tumor Awareness Month.

Doctors say Ryan will not likely make it to his 10 th birthday on May 24.

"[I will] rub his feet, help him with whatever he needs," his mom told CNN. "I just plan on being there and just loving him through this."