Nov 24, 2014
By Shira Klapper, Senior Writer/Editor
Children who receive stem cell transplantation (SCT) are at risk for long-term delays in cognitive functioning—but only if they are younger than three years of age before the transplant and if they receive total body irradiation (TBI) before the transplant. That’s according to the Journal of Clinical Oncology (JCO) study, “Cognitive Outcome After Pediatric Stem-Cell Transplantation: Impact of Age and Total-Body Irradiation,” published online, ahead of print, November 10.
Specifically, the study found that children who received SCT before the age of three showed cognitive delays one year post-treatment. However, the children who received TBI in addition to SCT continued to show those delays after the one-year time point, compared to children who received SCT alone.
“As a group, the youngest children who receive SCT show cognitive decline in the first year, regardless of whether they had TBI or not,” said Sean Phipps, PhD, Chair of Psychology at St. Jude Children’s Hospital. “However, subsequent to that first year, the children who were transplanted without TBI showed the ability to catch up, whereas the children who were transplanted with TBI remained stable and thus had a significantly lower IQ at year five.”
According to Dr. Phipps, previous studies that examined how SCT affects cognitive function among children with pediatric cancers have reported conflicting information.
“There were papers that suggested that younger children were at higher risk of having a poor outcome, but also papers that failed to show that,” said Dr. Phipps. “Likewise, there were papers suggesting that children who received total body irradiation were at higher risk of poor cognitive outcome and other studies that failed to show that.”
The current study attempted to address some of the issues with the methodology of previous studies, which often had a small sample size and used a retrospective design. This current study, by contrast, followed 315 children prospectively, from pre-SCT baseline and then over three additional time points: one year, three years, and five years post-SCT. The 315 patients in the study, who ranged in age from four months to 24 years old, were tested using IQ tests suited for their age groups. At the one-year time point, 183 children (58%) were alive and were able to continue taking part in the study.
A different model for thinking about cognitive decline in pediatric cancer
For Dr. Phipps, the findings in this study have challenged the way he thinks about the trajectory of cognitive decline among children with brain cancer and leukemia, diseases that are often treated with therapy to the central nervous system.
“We typically think of things in a purely linear fashion,” said Dr. Phipps. “If a child has a brain tumor, we assess them at the time of treatment and then a couple of years later, and then a couple of years after that. And when we follow the cognitive development over time, we generally draw a straight line showing that the further out you are from treatment, the greater the negative impact. But, the children in our study are showing a decline in the first year and then at least some of them start to get better over time.”
A strong case for early cognitive intervention
The study’s main finding—that children younger than three years of age are at the highest risk for long-term cognitive delays—makes a compelling argument for the need to increase the availability and intensity of cognitive interventions for these children.
“Children three and younger are, as a group, clinically at risk,” said Dr. Phipps. “Therefore, we should focus on rehab services and early interventions to stimulate them as much as we can during that first year. We typically do provide rehab services, but maybe we need to up the ante a bit to say that all hospitals should be providing these programs and maybe at a higher level of intensity.”
Sean Phipps, PhD, is a faculty member at St. Jude Children’s Research Hospital, where he serves as Chair of Psychology and the Endowed Chair in Behavioral Medicine.
Read the abstract of the original JCO article.
View the PDF of the original JCO article.
Phipps S, Zhang H, Huang Q, et al. Cognitive outcome after pediatric stem-cell transplantation: impact of age and total-body irradiation. J Clin Oncol. Epub 2014 Nov 10.
The Exclusive Coverage series on ASCO.org highlights selected research from JCO and JOP with additional perspective provided by the lead or corresponding author.
@ 2014 American Society of Clinical Oncology