SEARCH

SEARCH BY CITATION

Editor's note: This is Part 1 of a 2-part series on recent advances in pediatric cancers.

The fight against childhood cancers has made significant gains over the past decade, with survival rates as high as 80% to 90% reported for some diseases. Approximately 366,000 adults in the United States have survived the disease as children, and that number is on the rise.

Researchers at St. Jude Children's Research Hospital in Memphis, Tennessee, one of the leading treatment and research centers for childhood cancers, discuss some of those key achievements and the challenges that lie ahead.

Leukemia

Great progress has occurred in treating leukemia, the most common childhood cancer. Survival rates in patients with acute lymphoblastic leukemia are now at approximately 80%, while approximately 60% of patients survive the more aggressive acute myeloid leukemia. To achieve higher cure rates for these patients, researchers and physicians have turned to bone marrow transplantation (BMT).

“The success rate for BMT was less than 50% just 10 years ago, but it's now about 80%,” says Wing Leung, MD, PhD, chair of the department of bone marrow transplantation and cellular therapy at St. Jude's. That success rate is due to the fact that progress has occurred in all 3 stages of BMT: conditioning (chemotherapy given prior to the transplant), transplant, and posttransplant supportive care. With such a high volume of transplants (approximately 50,000 are performed worldwide each year), physicians have been able to perfect treatment while at the same time the overall science has improved, Dr. Leung says.

In conditioning, for example, instead of a “cookiecutter, one-size-fits-all approach,” centers now use different types of chemotherapy and radiotherapy depending on the individual patient; for example, they may reduce the amount of conditioning if they find that the patient already has problems with his or her heart, lung, or kidneys. At the same time, scientists have perfected grafting by finding ways to test potential donors for genes that are important in transplants, such as the killer-cell immunoglobulin-like receptor (KIR) gene family, which is known to protect healthy cells from spontaneous destruction.

In the posttransplant phase, laboratories are better able to monitor patients for viral infections by using molecular techniques that can identify early biomarkers for infection. They also can select specific patients who may not require the intense, toxic doses of antiviral medications.

In addition, real-time monitoring of patients enables physicians to respond quickly and change gears if treatments do not appear to be working. “In BMT, we can salvage patients who otherwise would have impending graft failure or leukemia relapse, which we would not have known 10 years ago,” Dr. Leung says.

Such major advances in pediatric oncology are largely attributed to the number of pediatric cancer patients who are enrolled in clinical trials: approximately 80% to 90%. The majority of those trials are run by cooperative groups, and as a result the majority of treatments in the field are truly evidence-based ones. In comparison, very few adult cancer patients (an estimated 5%) are enrolled in trials. Therefore, patient outcomes in many of those cases are not entered into any centralized database. Because pediatric cancers are fairly rare in comparison with adult cancers, pediatric specialists generally have to join together to learn any information about these diseases, Dr. Leung notes.

Natural Killer Cell Transplants

Another area of focus for researchers at St. Jude's is that of natural killer (NK) cells. These cells are among the 3 lymphocytes that are part of the body's immune system, but because they are less known and less common than B cells and T cells, the research has lagged. However, in recent years, scientists are beginning to understand the importance of NK cells in cancer control and treatment.

NK cell transplants may provide a less costly alternative to BMT, while at the same time causing no long-term side effects, according to Dr. Leung. Because NK cells are part of the body's natural immune system, and because the donor cells die after a month or 2, they do not cause side effects.

St. Jude's is leading a randomized, multicenter study that is evaluating whether NK cells can be used to replace BMT. In the study, which will wrap up by the end of 2015, investigators are using NK cells to treat approximately 100 patients with acute myeloid leukemia. Other participating centers include Harvard University, the University of Michigan, the Dana-Farber Cancer Institute, and Stanford University. Patients are given the option of either receiving their standard course of therapy for the particular stage of their disease (chemotherapy or BMT) or undergoing the NK cell treatment. “Preliminary results are encouraging, and if the study is effective, the next phase would be a national trial,” Dr. Leung says.

St. Jude researchers also are studying the NK cell transplants in very high-risk leukemia patients (including infants, for whom BMT is ineffective), in patients who have failed BMT, and in patients with solid tumors. The latter include patients with neuroblastoma who develop disease recurrence as well as those with general neuroblastoma, retinoblastoma, and Ewing sarcoma.

Part 2 of this series, which will be published in the October 1 issue, will explore more advances in childhood leukemia, childhood cancer survivorship, and brain tumor treatment.