She has been in remission for 11 months and is the first paediatric patient in a growing US trial that is showing signs of success after decades of research and now includes three other children and dozens of adults.
Her mother said Emily sometimes grapples with her newfound celebrity, which ballooned after the trial's results were first announced late last year.
"When we go to places where there are a lot of people, sometimes they want pictures with her, or sometimes just to touch her, so I think it gets a little overwhelming," Kari Whitehead told AFP.
Staying positive during treatment
For the most part though, Emily is happy to play with her dog, read, write and explore outdoors, thanks to an experimental treatment that saved her life after two relapses left doctors admitting they had no other options.
Now, the US researchers behind the method are expanding their quest for a next-generation cancer treatment that may require one dose in a lifetime, and may one day end the use of chemotherapy and bone marrow transplants.
While the word "cure" is something most experts would not whisper until a patient has lived at least five years illness-free, the field of research into targeted immune therapies is generating buzz.
Work at the University of Pennsylvania is supported by Swiss pharmaceutical giant Novartis, which last year announced an exclusive global deal to license chimeric antigen receptor (CAR) technologies for leukaemia and other cancers.
Novartis is also funding a $20 million center for research at the University of Pennsylvania as part of the agreement.
What the case study showed
The case studies that describe Emily's journey so far, and that of another 10-year-old girl who did not survive after trying the same adoptive T cell therapy, were detailed Monday in the New England Journal of Medicine.
Both girls suffered from acute lymphoblastic leukaemia (ALL), the most common form of childhood cancer. It is often curable, but theirs was a high-risk type that resists conventional treatments.
The new approach takes a patient's own white blood cells, called T cells, and genetically alters them with a receptor that allows them to recognise and kill cancer cells, according to Michael Kalos, who is part of the University of Pennsylvania team of researchers working on the project.
"The concept has been around for at least 50 years, and it has been tried in humans for about 20 years in different clinical trials, with limited success mostly because the T cells that were put into patients had a real hard time surviving in patients," Kalos told AFP.
Greater longevity was achieved when researchers began using a virus in the HIV family to serve as a vehicle for the gene that needs to enter the T cells, said Kalos.
The team, led by Carl June of the Abramson Cancer Center of the University of Pennsylvania, first published its results in 2011 on three adults who suffered from chronic lymphocytic leukaemia (CLL).
More than two years after treatment, two of the three are still living disease-free, and more than a dozen new patients have begun treatment.
A separate team of researchers at Memorial Sloan-Kettering Caner Center in New York also published a study last week in Science Translational Medicine detailing their work on five adult patients with ALL, the type Emily had.
Kalos said University of Pennsylvania researchers are seeing "very strong responses in most of the patients but in a small subset we are not seeing a response and we are trying to understand why that is the case.
"It could be the patient, it could be the product, it could be the tumors or it could be something totally different."
Early trails started in the US
In the meantime, early trials on adult pancreatic cancer patients and people with mesothelioma have already begun. For now, they are only in the United States, but the team hopes to expand globally.
The terrain is brand new. Every patient would need his or her own specialised treatment, and patients need to get antibody treatments to boost their immune systems for years, perhaps indefinitely, to guard against illness.
But, if the recent success continues, a treatment could be on the market within a few years, Kalos said.
"In our case, the data is looking so promising that we are hoping we can devise a phase II study that is so dramatic that we can go to (authorities) and say, 'This is something we'd like you to consider for approval.'"