(NEW YORK) -- Debbie Lewis will never forget the day she had to tell her daughter, Emily, that the 12-year-old was going to die.
Emily had been diagnosed since age 9 with Wilms tumor, a pediatric kidney cancer. The disease spread to her lungs shortly after, and she spent three years in and out of treatment, bouncing between progress and relapses.
Emily's doctors eventually told Lewis there was nothing more they could do. She and husband John had to tell Emily that the cancer had spread too far.
"Emily looked at me, and said, 'Mom, am I going to die?'" Lewis said.
As hard as the question was, Lewis said she never doubted that she should tell her daughter the truth. "She deserved to know as much as we knew, based on her ability to understand it," she said.
Two months later, in August 2009, Emily died in hospice care.
Few parents can imagine having to tell their child that his or her life will be cut short. Parents faced with the task are often reluctant to speak candidly about death, fearing that the news will spark fear or sap the child's will to live.
Dr. Justin Baker, director of palliative care at St. Jude Children's Research Hospital in Memphis, Tenn., said many parents ask him not to tell their child that they will die, even when the outlook is grim.
"They'll tell me, we just haven't been able to bring up the fact that he has cancer," Baker said. "My first question for them is, 'How much do you think your child already knows?'"
Children often have some idea that their condition is serious from listening to doctors, being aware of their own bodies or even researching their disease.
"Sometimes, they're already making up details in their mind about what's happening because they don't have an explanation," said Angela Locke, a child life specialist at Rainbow Babies and Children's Hospital in Cleveland. "Sometimes it's less scary when parents give the honest truth."
A conversation about death happens differently, depending on the age of the child and the cultural background and customs of the family. But experts say it's important for all parents to be as honest as they can about their child's condition and what the future holds.
Research suggests that those conversations are beneficial not only for children, but for parents as well. In 2004, Swedish researchers interviewed the families of more than 300 children who had died after a terminal illness, asking them if they had talked with their child about their death. Nearly 35 percent of parents reported that they had talked about death with their child, and none of them reported regretting those conversations.
Of the parents who reported not talking to their child about their death, 27 percent regretted that decision.
Copyright 2012 ABC News Radio