We know that Hodgkin lymphoma is one of the most commonly diagnosed cancers in adolescence in particular and we know that survivors of Hodgkin lymphoma are at risk of things like cardiovascular disease and neurologic conditions. But what we don’t know is whether or not they are at risk for neurocognitive impairment. We do know from preliminary data, though, that despite having no direct therapy to the central nervous system they do have some impairments relative to published norms.
What we wanted to do was characterise neurocognitive impairment in a large nationwide representative sample of Hodgkin lymphoma survivors in the US. So we used the Childhood Cancer Survivors Study which is a nationwide study of childhood cancer survivors and we looked at long-term survivors of Hodgkin lymphoma. These are survivors of childhood Hodgkin lymphoma that are, on average, about twenty years from their cancer diagnosis.
What we found was that compared to sibling controls they were at a significant increased risk of impairment in things like memory and organisation and task efficiency which is a measure of processing speed and attention. They were at a significant increased risk compared to their sibling controls. What was interesting, though, was when we went to look for treatment effects we really didn’t see any significant associations. Instead, what we saw was that modifiable risk factors like smoking and physical activity were associated with cognitive impairment. We also saw that chronic health conditions were associated with an increased risk of cognitive impairment, specifically cardiovascular conditions and neurologic conditions like stroke conferred an increased risk of neurocognitive impairment.
I told you that these were long-term survivors about twenty years from diagnosis but on average only about 35 years old. So this suggests to us that the treatment may be conferring an increased risk of chronic health conditions that then increased their risk for neurocognitive impairment due to some sort of accelerated aging phenomenon that is also causing some cognitive aging.
But what we think is really important about these findings is that it was modifiable and preventable risk factors that were associated with neurocognitive impairment. So research on things like physical activity interventions as well as preventing or managing chronic health conditions well may help us understand how to prevent or mitigate some neurocognitive impairments in this population.
How might the historical differences in treatment affect the long term status of these patients?
These survivors from the Childhood Cancer Survivors Study were actually diagnosed between 1970 and 1999 which means that their treatment protocols that they were on do differ a little bit from the treatment protocols that we use today. However, many of them did receive things like chest radiation and anthracyclines which are still used prominently in treatment regimens today. So we believe that trying to find a way to prevent chronic health conditions in this population could have a huge impact on the prevention of neurocognitive decline in this population as they age. It will be interesting to see as we introduce more targeted agents and immunotherapies in this group how those will also affect their neurocognitive functioning, both during treatment and as they go on to live the rest of their healthy lives, hopefully.