Longitudinal cohort studies have provided insight into predictors of cognitive decline among long-term survivors of CNS tumors. A report from St. Jude Children's Research Hospital showed cognitive decline after conformal radiation therapy in 78 children younger than 20 years (mean, 9.7 years) with low-grade glioma treated with 54 Gy (see Figure 3). Age at time of irradiation was more important than radiation dose in predicting cognitive decline with children younger than 5 years showing the most cognitive decline. Neurocognitive deficits have also been linked to poor social outcomes including poor social adjustment, problems with peer relationship, and withdrawn/depressed behaviors among survivors of pediatric embryonal tumors.
Figure 3. Modeled intelligence quotient (IQ) scores after conformal radiation therapy (CRT) by age for pediatric low-grade glioma. Age is measured in years, and time is measured in months after the start of CRT. Thomas E. Merchant, Heather M. Conklin, Shengjie Wu, Robert H. Lustig, and Xiaoping Xiong, Late Effects of Conformal Radiation Therapy for Pediatric Patients With Low-Grade Glioma: Prospective Evaluation of Cognitive, Endocrine, and Hearing Deficits, Journal of Clinical Oncology, volume 27, issue 22, pages 3691-3697. Reprinted with permission. © (2009) American Society of Clinical Oncology. All rights reserved.
Glutathione S-transferase M1 and T1 gene polymorphisms may predict patients with medulloblastoma who are more likely to experience neurocognitive toxicity secondary to radiation.
Acute lymphoblastic leukemia (ALL)
One of the great medical success stories of the past generation is how advances in the treatment of ALL have dramatically improved survival. With the recognition that CNS relapse was common among children in bone marrow remission, presymptomatic CNS radiation and intrathecal chemotherapy were introduced into the treatment of children with ALL in the 1960s and 1970s. The increase in cure rates for children with ALL over the past decades has resulted in greater attention to the neurocognitive morbidity and quality of life of survivors. The goal of current ALL treatment is to minimize adverse late effects while maintaining high survival rates. Patients are stratified for treatment according to their risk of relapse. Cranial radiation is reserved for children (less than 20%) considered at high risk for CNS relapse.