Janzen, Laura

Abstract PURPOSE By reducing dose to normal brain tissue, proton radiotherapy (PRT) may lessen neurocognitive risk traditionally associated with photon radiotherapy (XRT). We examined change in neurocognitive scores over time in pediatric medulloblastoma patients treated with PRT versus XRT. METHODS Neurocognitive scores from 79 patients (37 PRT, 42 XRT) were examined. Patients were treated between 2007–2018 on the same treatment protocols that differed only by craniospinal modality (PRT versus XRT). Change in scores over time since diagnosis were compared between groups. RESULTS Groups were similar on most demographic/clinical variables: sex (67.1% male), age at diagnosis (mean 8.6 years), CSI dose (median 23.4 Gy), length of follow-up (mean 4.3 years), and parental education (mean 14.3 years). Boost dose (p<0.001) and margin (p=0.001) differed between groups. Adjusting for covariates, the PRT group exhibited superior outcomes in global IQ, perceptual reasoning, and working memory versus the XRT group (all p<0.05). The XRT group exhibited significant decline in global IQ, working memory, and processing speed (all p<0.05). The PRT group exhibited stable scores in all domains except processing speed (p=0.003). Posterior fossa syndrome imparted risk independent of modality. CONCLUSION This is the first study comparing neurocognitive trajectories between pediatric patients treated for medulloblastoma with PRT versus XRT on comparable, contemporary protocols. PRT was associated with more favorable neurocognitive outcomes in most domains compared to XRT, although processing speed emerged as vulnerable in both groups. This is the strongest evidence to date of an intellectual sparing advantage with PRT in the treatment of pediatric medulloblastoma.

PURPOSE Proton radiotherapy (PRT) may lessen the neuropsychological risk traditionally associated with cranial radiotherapy for the treatment of pediatric brain tumors by reducing the dose to normal tissue compared with that of photon radiotherapy (XRT). We examined the change in intellectual scores over time in patients with pediatric medulloblastoma treated with craniospinal PRT versus XRT. METHODS Intelligence test scores were obtained for a sample of pediatric patients treated between 2007 and 2018 on the same medulloblastoma protocols that differed only in radiotherapy modality (PRT v XRT). Growth curve analyses compared change in scores over time since diagnosis between groups. RESULTS Longitudinal intelligence data from 79 patients (37 PRT, 42 XRT) were examined. Groups were similar on most demographic/clinical variables, including sex (67.1% male), age at diagnosis (mean, 8.6 years), craniospinal irradiation dose (median, 23.4 Gy), length of follow-up (mean, 4.3 years), and parental education (mean, 14.3 years). Boost dose ( P < .001) and boost margin ( P = .001) differed between groups. Adjusting for covariates, the PRT group exhibited superior long-term outcomes in global intelligence quotient (IQ), perceptual reasoning, and working memory compared with the XRT group (all P < .05). The XRT group exhibited a significant decline in global IQ, working memory, and processing speed (all P < .05). The PRT group exhibited stable scores over time in all domains with the exception of processing speed ( P = .003). CONCLUSION To our knowledge, this is the first study to compare intellectual trajectories between pediatric patients treated for medulloblastoma with PRT versus those treated with XRT on comparable, contemporary protocols. PRT was associated with more favorable intellectual outcomes in most domains compared with XRT, although processing speed emerged as a vulnerable domain for both groups. This study provides the strongest evidence to date of an intellectual sparing advantage with PRT in the treatment of pediatric medulloblastoma.