Lancet: Brain-tumor radiotherapy may reduce cognitive function
Even low doses of radiotherapy that are regarded as safe may contribute to progressive cognitive decline in patients with low-grade glioma (LGG) brain tumors, according to a study published online Aug. 9 that will appear in the September edition of Lancet Neurology.

LGG brain tumors are the most common type of brain cancer. Early or delayed radiotherapy is the most common treatment, but many questions remain about the best treatment strategy, according to the authors. Radiotherapy can cause damage to the brain over time and because the average survival time for patients with LGG is 10 years, the patients are at considerable risk of acquiring late or delayed radiation injuries.

In a previous study, the authors found that at an average of six years after diagnosis, high-level radiation treatment and the tumors were associated with cognitive impairment. However, Linda Douw, MD, from VU University Medical Center in Amsterdam, Netherlands, and colleagues noted that the effects of local radiotherapy on cognitive function in long-term survivors of LGG are not known.

In this study, Douw and her team reported the long-term radiological and cognitive abnormalities in survivors of LGG from the original study. They performed a follow-up cognitive assessment on 65 patients who had stable disease since the first assessment (of whom around half had received radiotherapy) at an average of 12 years after treatment.

In total, the authors reported that 27 percent of patients who did not have radiotherapy had cognitive disability, compared with 53 percent of those who had been given radiotherapy.

Overall, the researchers reported that patients given radiotherapy had lower ability at attentional functioning, executive functioning, and information processing speed than patients not given radiotherapy. Findings also showed that patients who did not have radiotherapy showed stable radiological and cognitive status.

"By contrast with the results of our earlier study, the current results indicate that radiotherapy is associated with long-term cognitive deterioration, regardless of fraction dose...[and indicate that] all surviving patients who had radiotherapy are at risk of developing attentional problems," not just those who were given a high-level dose, the authors wrote.

They concluded that treating patients who have LGG with radiotherapy should be considered carefully and suggest that deferring treatment might be the treatment strategy that is most beneficial to cognitive status and quality of life.

In an accompanying commentary, Paul Brown, MD, and Jane Cerhan, MD, from the Mayo Clinic in Rochester, Minn., pointed out that there have been substantial improvements in radiotherapeutic techniques since the 1970s when the treatment period in the study started, and caution that it is therefore not possible to make firm generalizations about the risks of modern radiotherapy from these results.

Brown and Cerhan called for more trials to assess the effects of modern radiotherapy techniques on cognitive function in patients with LGG.