"In two weeks he was weaned of all the nausea drugs, and he was eating again and sitting up in and laughing," according to Hyde, who said doctors called his son's recovery "a miracle."
NYU's Granowetter said cannabis "certainly can increase appetite and improve mood...but the idea that it can cure cancer is ludicrous."
She said the drug is most effective in teens who have previously used marijuana. "In young adults or children who have not had it before, it can make them paranoid."
"It's awfully hard to gauge if a child would have a bad reaction," according to Granowetter, who said she would welcome clinical trials on children.
"We know from research that 30 to 60 percent of parents with children are giving them alternative meds like vitamins, shark tooth and herbs from Chinatown," she said. "That's why we spend a lot of time asking parents what else they are giving kids and trying to be non-judgmental and work with them and guide them."
She said most pediatric oncologists are "open-minded" about alternative treatments.
Mike Hyde said he did eventually tell the Utah doctors, who were surprised by how Cash bounced back with no permanent organ damage. They say the boy has a 50 to 80 percent chance that the cancer will come back, according to Hyde, who has since started a foundation to help children with cancer.
"We were told I was one of the best dads," said Hyde, who lived with his wife and their other 6-year-old son in a camper in a parking lot for the nine months of treatment. "Every encounter in Salt Lake City, we were positive and never quit fighting. I was told he was going to die, but I knew he hadn't stopped the fight."
For more information on Cash and how to help other children with cancer, go to the Cash Hyde Cancer Foundation.