Introduction
It is well documented that pediatric brain tumor survivors are at risk
for poor long-term social outcomes relative to same-age peers. Reviews
of social outcomes in survivors have highlighted an increased risk for
social skill deficits and poor long-term social adjustment, including
social isolation and victimization.1,2 Recent studies
examining specific components of social adjustment, such as peer
relationships, have found that survivors are less likely to be able to
name a friend than children with non-central nervous system
tumors3 and are at high risk of having no reciprocated
best friendship nominations in sociometric analyses.4Caregiver ratings also highlight social concerns among survivors, with
poor social outcomes rated as among the most impactful late effects in
survivorship.5 This has prompted recent intervention
efforts to support survivor social skills and overall social
functioning.6,7 However, much remains unknown with
respect to predictors of social adjustment among survivors.
Given known cognitive deficits following cancer and cancer-related
treatments,8 as well as the known interrelationship of
cognitive and social functioning, 9,10 it is likely
that cognitive skills are drivers of survivor social outcomes. In fact,
a recent review highlighted the identification of determinants of social
impairment as one of the most important emerging areas in survivorship
research in this population.11 Schulte and
colleagues12 found that cognitive impairment mediated
the association between cranial radiation therapy and survivor social
outcomes, including quality of social interactions and social
withdrawal. Other researchers have examined more specific cognitive
outcomes. For example, Dejardins and colleagues13found an association between metacognitive skills and parent ratings of
survivor social skills (e.g., cooperation, assertiveness, and
self-control). Studies have also examined attention skills as important
predictors of social outcomes, highlighting inattention and
parent-reported attention problems as significant predictors of survivor
social problems.14,15 Continued investigation into
known cognitive skill deficits among survivors (e.g., processing speed,
executive functioning) and the impact of these deficits on specific
aspects of social functioning is warranted, particularly given known
associations between cognitive predictors and social outcomes in other
pediatric traumatic and acquired brain injury
populations16-18 as well as autism spectrum disorder.19, 20
In addition to examining specific cognitive predictors, an investigation
of survivor social outcomes should consider different radiation
treatment modalities and the neurocognitive sparing potential of proton
radiation therapy (PRT). Given the unique physical properties of PRT,
maximum radiation dose is delivered to the tumor, with less entrance
dose and no exit dose compared to photon radiation (XRT).21-23 Thus, with the sparing of more healthy brain
tissue, it is suggested that PRT may yield better neurocognitive
outcomes compared to XRT. The few comparison studies published to date
are suggestive of neurocognitive sparing with PRT, with evidence for
higher IQ, processing speed, perceptual reasoning, executive
functioning, and fine motor coordination among survivors treated with
PRT versus XRT.24-27 However, continued comparison of
clinically meaningful outcomes across radiation groups is warranted.
Of these clinically meaningful outcomes, social functioning remains
particularly understudied. If indeed PRT offers a neuroprotective
benefit over XRT, it is plausible that better neurocognitive outcomes
among survivors treated with PRT would support better social outcomes
compared to those treated with XRT. However, this relationship between
therapy modality, neurocognitive outcomes, and social functioning has
not been directly examined. In their recent study comparing PRT and XRT
treatment groups, Gross and colleagues26 found better
parent-rated social functioning for patients treated with PRT relative
to XRT on a broadband adaptive skills rating measure. In another study
examining quality of life more broadly, PRT patients were found to have
higher quality of life ratings in the psychosocial domain relative to
XRT patients.28 While these findings are promising,
cognitive predictors were not examined.
The present study offers the first known examination of a wide range of
neurocognitive skills as predictors of peer relationships and social
skills between pediatric brain tumor survivors treated with PRT versus
XRT in late survivorship. We hypothesized that survivors treated with
PRT would outperform those treated with XRT on cognitive measures and
would be rated by caregivers as having better social outcomes. We also
hypothesized that cognitive outcomes would predict survivor peer
relations and social skills.