Proton therapy and limited surgery for paediatric and adolescent patients with craniopharyngioma (RT2CR): a single-arm, phase 2 study

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. 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. 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). 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.

To determine whether proton radiotherapy has clinical advantages over photon radiotherapy, we modeled the dose characteristics of both to critical normal tissue volumes using data from patients with four types of childhood brain tumors. Three-dimensional imaging and treatment planning data, including targeted tumor and normal tissues contours, were acquired for 40 patients, 10 each with optic pathway glioma (OPG), craniopharyngioma (CR), infratentorial ependymoma (EP), or medulloblastoma (MB). Dose-volume data were collected for the entire brain, temporal lobes, cochlea, and hypothalamus from each patient. The data were averaged and compared based on treatment modality (protons vs. photons) using dose-cognitive effects models. Outcomes were estimated over 5 years. Relatively small critical normal tissue volumes such as the cochlea and hypothalamus may be spared from radiation exposure when not adjacent to the primary tumor volume. Larger normal tissue volumes such as the supratentorial brain or temporal lobes receive less of the low and intermediate doses. When applied to longitudinal models of radiation dose-cognitive effects, these differences resulted in clinically significant higher IQ scores for patients with MB and CR and academic reading scores in patients with OPG. Extreme differences between proton and photon dose distributions precluded meaningful comparison of protons and photons for patients with EP. Differences in the overall dose distributions, as indicated by modeling changes in cognitive function, showed that a reduction in the lower-dose volumes or mean dose would have long-term, clinical advantages for children with MB, CR, and OPG. (c) 2008 Wiley-Liss, Inc.

Cranial irradiation in pediatric patients is associated with serious long-term adverse effects. We sought to determine whether both three-dimensional conformal proton radiotherapy (3D-PRT) and intensity-modulated proton therapy (IMPT) compared with intensity-modulated radiotherapy (IMRT) decrease integral dose to brain areas known to harbor neuronal stem cells, major blood vessels, and other normal brain structures for pediatric patients with craniopharyngiomas. IMRT, forward planned, passive scattering proton, and IMPT plans were generated and optimized for 10 pediatric patients. The dose was 50.4 Gy (or cobalt Gy equivalent) delivered in 28 fractions with the requirement for planning target volume (PTV) coverage of 95% or better. Integral dose data were calculated from differential dose-volume histograms. The PTV target coverage was adequate for all modalities. IMRT and IMPT yielded the most conformal plans in comparison to 3D-PRT. Compared with IMRT, 3D-PRT and IMPT plans had a relative reduction of integral dose to the hippocampus (3D-PRT, 20.4; IMPT, 51.3%*), dentate gyrus (27.3, 75.0%*), and subventricular zone (4.5, 57.8%*). Vascular organs at risk also had reduced integral dose with the use of proton therapy (anterior cerebral arteries, 33.3*, 100.0%*; middle cerebral arteries, 25.9%*, 100%*; anterior communicating arteries, 30.8*, 41.7%*; and carotid arteries, 51.5*, 77.6*). Relative reduction of integral dose to the infratentorial brain (190.7*, 109.7%*), supratentorial brain without PTV (9.6, 26.8%*), brainstem (45.6, 22.4%*), and whole brain without PTV (19.4*, 34.4%*) were recorded with the use of proton therapy. (*Differences were significant based on Friedman's test with Bonferroni-Dunn correction, α = 0.05) The current study found that proton therapy was able to avoid excess integral radiation dose to a variety of normal structures at all dose levels while maintaining equal target coverage. Future studies will examine the clinical benefits of these dosimetric advantages. Published by Elsevier Inc.