Recent decades have seen
huge strides in treating childhood cancer, but certain types of tumours remain
difficult to treat and are often deadly.
That's the frustrating fact
at the heart of a meeting held this week by the American Association for Cancer
Research. Paediatric cancer experts gathered in San Diego to discuss recent
advances in understanding childhood tumours and the obstacles to improving
"The exciting thing is
that we're in an era of unprecedented discovery," said Dr John Maris,
referring to recent research on the genetic underpinnings of childhood cancers.
"But there's still a huge amount of work to be done."
One of the challenges in paediatric
cancer research is that, thankfully, it's relatively rare for children to
develop cancer, said Maris, who directs the Centre for Childhood Cancer
Research at Children's Hospital of Philadelphia.
In the United States, one
or two out of every 10 000 kids develop cancer each year, according to the US
National Cancer Institute. It amounts to around 12 000 cases of childhood
cancer and about 1 500 deaths annually.
Dr James Downing, deputy
director of St Jude Children's Research Hospital in Memphis, Tennessee, said that's
a very small amount compared with the number of adults diagnosed with cancer.
As a result, Downing said,
government funds and drug companies' interests are largely focused on adult
"There are also very
important practical considerations, because these are children," Maris
Drugs of any kind typically
are tested first in adults to help shield kids from toxic effects of
experimental therapies. Safety concerns, plus limited resources and other
issues, can slow progress.
"In paediatrics, we
have to be very, very careful about prioritising what we test," Maris
In some cancer areas, there
have been huge success stories. A major example is the blood cancer acute
lymphoblastic leukaemia (ALL), the most common type of cancer in children. In
the early 1960s, only about 4% of US children diagnosed with ALL were alive
five years later. Now that number exceeds 90%.
Overall, the five-year
survival rate from all childhood cancers combined has risen from around 60% in
the mid-1970s to more than 80% in more recent years, according to the cancer
Downing said, however, that
cancer still kills more kids under age 15 than any other disease. And certain
types remain stubbornly resistant to everything doctors have thrown at them.
"There's a subset of
cancers where we just have not made progress," Maris said.
One example is a tumour of
the brain stem called pontine glioma a "terrible disease", Downing
said, that usually kills within a year.
Another example is
neuroblastoma, a cancer of the nerve tissue in various parts of the body that
usually arises before age 5. Many more kids survive the disease than in years
past, but the chances depend in part on the child's age.
Infants have a high cure rate,
with about 90% alive five years later; that dips to 68% among children
diagnosed between the ages of 1 and 4, according to the cancer institute.
The biology of a child's
neuroblastoma is also key. "We used to think all neuroblastoma were the
same," Maris said. "They're not."
Maris and his colleagues
found that mutations in a gene called ALK are behind a rare form of
neuroblastoma that runs in families.
An oral cancer drug already
tested and approved for certain cases of lung cancer in adults targets ALK. In
early trials, the drug, called crizotinib, led to remission in kids with the
rare form of neuroblastoma and children with an uncommon, aggressive type of
At St Jude, Downing and his
colleagues have been working on a project to "decode" the genomes of
more than 600 children with cancer in an attempt to gain a better understanding
of the genetic origins of various tumours. They've found specific gene
mutations in certain gliomas, neuroblastoma and rare subtypes of leukaemia that
they hope will someday lead to better treatments.
But even with highly
curable cancers, such as ALL, safer treatments are needed. The chemotherapy,
radiation and other therapies used to battle kids' cancer can have unfortunate
side effects years later including other cancers and heart and lung damage.
"When you're talking
about children, a cure is not enough," Maris said.
Both Maris and Downing
pointed to better funding as a vital need. "We need advocacy at the
legislative level to make sure paediatric cancers aren't unwittingly
discriminated against," Maris said.
Public support including
donations to foundations supporting paediatric cancer research can also help,
Downing said. "This can't get done without support from the general
public," he said.
The National Cancer
Institute has more on childhood
(Picture: Cancer cell from Shutterstock)