Challenges Remain for Kids With Cancer
More children are being treated successfully for cancer. Yet researchers continue searching for new therapies that will help kids who don't respond to standard treatments.
By Cameron Walker
Petekarici / iStock
Everything looked fine at Emily Whitehead’s checkup in May 2010. Yet in the weeks that followed, the 5-year-old said her legs were hurting, and her parents noticed bruises, too. At first, they chalked up their daughter’s symptoms to growing pains and childhood scrapes. Then one night, Emily’s aching legs woke her up. The next day, the Philipsburg, Pennsylvania, family returned to their pediatrician. A blood test revealed Emily had acute lymphoblastic leukemia (ALL).
ALL is considered one of the most curable childhood cancers, but that was not always the case. In the 1960s, only 10 percent of children with ALL survived for five years or more; now, nearly 90 percent of children treated with the standard chemotherapy survive long term. For the estimated 10,270 children in the U.S. who will be diagnosed with cancer in 2017, standard treatments, including chemotherapy and radiation, will successfully bring many of them into long-term remission.
“Childhood cancer is often pointed to as a success story, and in many respects, it is,” says Peter C. Adamson, a pediatric hematologist-oncologist at Children’s Hospital of Philadelphia (CHOP). But successes don’t tell the whole story, he says. Between 15 and 20 percent of children with ALL relapse after chemotherapy, and other childhood cancers have not seen a great improvement in survival. Nearly 1,800 children and teens still die each year from cancer, the leading cause of death by disease in this age group in the U.S.
Emily’s leukemia went into remission
in the summer of 2010 after a month of chemotherapy. She continued to get monthly chemotherapy and blood tests, but in October 2011, she relapsed while still in treatment. Doctors scheduled her for a bone marrow transplant in February 2012, but she relapsed again three weeks before the scheduled date. Doctors at Penn State Children’s Hospital in Hershey, Pennsylvania, continued to treat her with chemotherapy
to prepare her for the bone marrow transplant, but after a month, they concluded that Emily’s cancer was too aggressive. They were out of treatment options.
Researchers like Adamson are working to bring new treatments to the children who need them and to better understand childhood cancer by analyzing its genetics.
“Developing new treatments that are targeted has to be a priority for us,” says Adamson. “We’ve taken the drugs that we use today as far as we can take them.”
Adult cancers are different from those found in children, and that can present research and treatment challenges. Adults are usually diagnosed with solid tumors, while the most common childhood cancers are blood cancers, such as leukemia, and brain and spinal cord cancers. The underlying triggers for cancer are also different for children. Some adult cancers have risk factors that accumulate over a lifetime, but for childhood cancers, changes that provide the perfect storm for cancer happen in the child’s very first years or even before birth. (See “Monitoring Children for Heritable Cancers
“We normally think of cancer as a disease of old age,” when genetic mutations and lifestyle factors that increase risk have had time to accumulate, says Elaine Mardis, a cancer genomics researcher at the Nationwide Children’s Hospital Institute for Genomic Medicine in Columbus, Ohio. In most childhood cancers, Mardis says, “you don’t find a lot of mutations.” This means only a small number of the new drugs being developed to target mutations in adult cancers may be effective in treating childhood cancers.
To understand what triggers childhood cancer, scientists have started to look at the DNA of children with the disease. In 2010, researchers from Washington University School of Medicine in St. Louis and St. Jude Children’s Research Hospital in Memphis, Tennessee, launched a five-year effort co-led by Mardis to study the genomes of both cancer cells and normal cells in more than 800 children with cancer. The results have shed light on how the cancer genome varies among childhood cancer types and different forms of the same cancer. Research has also uncovered that many childhood cancers feature genes that are fused together to allow the cancer cell to make new proteins, called fusion oncoproteins, that can trigger brain tumors, leukemia, and bone and muscle tumors. These fusion onco-proteins are promising
targets for treatments, Mardis says.
“We have a rather good understanding of many of the genomic changes that occur in childhood cancers, but a much more limited understanding of what the changes are when our treatments fail,” says Adamson. For more insights into what makes a child relapse, Adamson and his colleagues launched the Pediatric MATCH trial in July 2017. This trial will sequence the tumor DNA of children whose cancer has not improved or has relapsed after standard therapy. Children whose tumors are a match for treatment will receive one of eight targeted drugs. In the process, researchers will learn more about how each treatment works on genomic variants of the cancer.
“The hope is that doing studies that take us to the next level to understand how these are driving childhood cancers will open the door to potential treatments,” Adamson says.
Immunotherapy for Children
Cancer immunotherapy enhances the ability of the body’s immune system to attack cancer cells. Checkpoint inhibitors, a group of immunotherapy drugs approved by the U.S. Food and Drug Administration (FDA) to treat adult cancers, appear to be less effective in children, at least when used alone. But other types of immunotherapy for children have had notable successes.