A study of children treated for low-grade gliomas, the most common pediatric brain tumors, found that nearly 90% were alive after 20 years and that few died of the tumor as adults. At the same time, children who received radiotherapy as part of their treatment had significantly lower survival rates than those who did not. The researchers, from Dana-Farber/Boston Children's Cancer and Blood Disorders Center in Boston, Massachusetts, say the results are, to their knowledge, the first comprehensive, large-scale study of such patients.
The findings were consistent regardless of whether surgeons could successfully remove a child's entire tumor or only part of it. As a result, the radiotherapy itself may explain the survival difference, the authors say.
Delivery of radiation has long been linked to a variety of harmful long-term effects. Many major hospitals have nearly eliminated treating patients with low-grade gliomas with radiotherapy, but the amount of radiation used by other hospitals varies, according to the study's senior author, Peter Manley, MD.
The researchers were unable to determine the precise mechanism driving the association between radiotherapy and reduced long-term survival, such as second cancers or other radiation-induced toxicities. Nevertheless, because of the excellent long-term survival noted among the patients studied, they suggest that physicians treating patients with pediatric low-grade glioma should prioritize reducing causes of long-term toxicity. Dr. Manley adds that multiple options are available for treating these children and these approaches should be exhausted before radiotherapy is used.
Dr. Manley and his colleagues analyzed the Surveillance, Epidemiology, and End Results program data from the National Cancer Institute on more than 4000 patients diagnosed with a pediatric low-grade glioma between 1973 and 2008. Although nearly 90% of pediatric survivors were still alive 20 years after treatment, only approximately 70% of those treated with radiotherapy were still alive at that time.
Other factors affecting survival included tumor location (cerebellum or not), tumor type (pilocytic or not), aggressiveness of the tumor (grade 1 vs grade 2), year of diagnosis (before or after 1990), and age of the patient at diagnosis (younger than 2 years vs older than 2 years). These factors were found to have less of an effect on long-term survival compared with radiotherapy, according to the team's multivariate analysis.