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.