The purpose of this study was to analyze renal late effects after proton beam therapy (PBT) for pediatric malignant tumors. A retrospective study was performed in 11 patients under 8 years of age who received PBT between 2013 and 2018. The kidney was exposed in irradiation of the primary lesion in all cases. Kidney volume and contour were measured on CT or MRI. Dose volume was calculated with a treatment-planning system. The median follow-up was 24 months (range, 11–57 months). In irradiated kidneys and control contralateral kidneys, the median volume changes were −5.63 (−20.54 to 7.20) and 5.23 (−2.01 to 16.73) mL/year; and the median % volume changes at 1 year were −8.55% (−47.52 to 15.51%) and 9.53% (−2.13 to 38.78%), respectively. The median relative volume change for irradiated kidneys at 1 year was −16.42% (−52.21 to −4.53%) relative to control kidneys. Kidneys irradiated with doses of 10, 20, 30, 40, and 50 GyE had volume reductions of 0.16%, 0.90%, 1.24%, 2.34%, and 8.2% per irradiated volume, respectively. The larger the irradiated volume, the greater the kidney volume was lost. Volume reduction was much greater in patients aged 4–7 years than in those aged 2–3 years. The results suggest that kidneys exposed to PBT in treatment of pediatric malignant tumor show continuous atrophy in follow-up. The degree of atrophy is increased with a higher radiation dose, greater irradiated volume, and older age. However, with growth and maturation, the contralateral kidney becomes progressively larger and is less affected by radiation.

To compare late renal effects in pediatric and adult patients with malignancies after PBT involving part of the kidney. A retrospective study was conducted to assess changes in renal volume and function in 24 patients, including 12 children (1–14 years old) and 12 adults (51–80 years old). Kidney volumes were measured from CT or MRI images during follow-up. Dose-volume histograms were calculated using a treatment planning system. In children, the median volume changes for the irradiated and control kidneys were −5.58 (−94.95 to +4.79) and +14.92 (−19.45 to +53.89) mL, respectively, with a relative volume change of −28.38 (−119.45 to −3.87) mL for the irradiated kidneys. For adults, these volume changes were −22.43 (−68.7 to −3.48) and −21.56 (−57.26 to −0.16) mL, respectively, with a relative volume change of −5.83 (−28.85 to +30.92) mL. Control kidneys in children exhibited a marked increase in size, while those in adults showed slight volumetric loss. The percentage of irradiated volume receiving 10 Gy (RBE) (V10) and 20 Gy (RBE) (V20) were significantly negatively associated with the relative volume change per year, especially in children. The CKD stage based on eGFR for all patients ranged from 1 to 3 and no cases with severe renal dysfunction were found before or after PBT. Late effects on the kidneys after PBT vary among age groups. Children are more susceptible than adults to significant renal atrophy after PBT. V10 and V20 might serve as predictors of the degree of renal atrophy after PBT, especially in children. PBT has a minimal impact on deterioration of renal function in both children and adults.

Background/Objectives: PBT enables precise targeting of tumors, which reduces side effects on surrounding organs, with particularly significant benefits for pediatric tumors. However, the efficacy of PBT compared to photon RT for pediatric medulloblastoma is unclear. A meta-analysis to assess the efficacy of PBT vs. photon RT for this disease was performed. Methods: Articles focusing on postoperative primary medulloblastoma from 1990 to 2022 were systematically reviewed and survival outcomes were extracted for medulloblastoma treated with PBT or photon RT. Meta-regression was used to identify predictive factors for treatment outcomes, including modality (PBT vs. photon RT), disease risk classification, gender, and age. Results: From 935 records, 18 articles were included (14 on photon RT, with 6 focusing on high-risk cases, and 4 on PBT). In standard-risk cases, the 1-, 3-, and 5-year overall survival (OS) rates were 95.5% (95% CI: 87.2–98.4%) vs. 96.7% (95% CI: 93.5–98.4%) (p = 0.1210); 89.8% (95% CI: 85.3–92.9%) vs. 88.0% (95% CI: 83.7–91.3%) (p = 0.5416); and 82.9% (95% CI: 76.6–87.6%) vs. 82.4% (95% CI: 77.2–86.5%) (p = 0.8313), respectively. For high-risk cases, the OS rates were 88.9% (95% CI: 85.5–91.6%); 73.6% (95% CI: 60.9–82.8%); and 68.6% (95% CI: 56.1–78.3%), respectively. The 1-, 3-, and 5-year progression-free survival (PFS) rates in standard-risk cases were 95.2% (95% CI: 91.8–97.2%) vs. 93.8% (95% CI: 89.4–96.5%) (p = 0.5275); 82.9% (95% CI: 77.3–87.2%) vs. 82.5% (95% CI: 80.1–84.7%) (p = 0.4294); and 79.6% (95% CI: 73.1–84.6%) vs. 77.0% (95% CI: 72.7–80.8%) (p = 0.3938), respectively. For high-risk cases, the PFS rates were 83.5% (95% CI: 77.0–88.3%); 64.8% (95% CI: 53.2–74.2%); and 60.4% (95% CI: 47.0–71.4%), respectively. Meta-regression analysis indicated no significant differences in 1- to 5-year OS and PFS between radiation modalities. Standard-risk cases were significantly associated with better OS and PFS. Younger age was significantly associated with 1- and 2-year OS and 1-year PFS, and male gender was significantly associated with 3-year OS and 3-year PFS. Conclusions: Postoperative irradiation for pediatric medulloblastoma using PBT has a therapeutic effect comparable to that of photon RT. This suggests that PBT is a useful option among RT modalities for medulloblastoma.

Background/Objectives: The optimal radiotherapy modality for World Health Organization (WHO) Grade 1 meningioma remains uncertain. Proton therapy offers dosimetric advantages through reduced radiation exposure to normal brain tissue, but comparative clinical data across contemporary radiotherapy modalities are limited. We performed a systematic review and meta-analysis comparing local control (LC) outcomes among conventionally fractionated proton therapy (CF-PT), conventionally fractionated photon radiotherapy (CF-Photon RT), Linac-based stereotactic radiosurgery/radiotherapy (Linac-based SRS/SRT), and Gamma Knife radiosurgery (GKRS). Methods: A systematic literature search of PubMed (2000–2024) was conducted to identify studies reporting LC for WHO Grade 1 meningioma treated with CF-PT, CF-Photon RT, Linac-based SRS/SRT, or GKRS. Random-effects meta-analyses were performed to estimate pooled 1- to 5-year LC rates. Random-effects meta-regression analyses were conducted using modality, age, sex, and gross tumor volume (GTV) as covariates. Results: Twenty-four studies comprising 4673 patients were included in the meta-analysis. Median GTVs were larger in the CF-PT and CF-Photon RT cohorts than in the Linac-based SRS/SRT and GKRS cohorts. All modalities achieved excellent LC: 5-year LC rates were 95.9% for CF-PT, 93.0% for CF-Photon RT, 95.3% for Linac-based SRS/SRT, and 89.8% for GKRS. Meta-regression showed no significant association between modality or GTV and LC. In the CF-PT cohort, 5-year overall survival was 93.1%. Conclusions: Major radiotherapy modalities achieved excellent and comparable LC. Notably, CF-PT and CF-Photon RT maintained favorable LC despite being used for larger tumors than stereotactic approaches. Future studies are needed to evaluate long-term tumor control and treatment-related toxicity to define optimal treatment strategies.

Background: Sinonasal neuroendocrine carcinoma (SNEC) is an extremely rare malignancy, and, to date, no clinical reports have detailed the use of proton beam therapy (PBT) for this disease. The present study describes the clinical courses of patients with SNEC treated with PBT and highlights the advantages of PBT. Methods: In this retrospective study, we included patients with pathologically confirmed SNEC without distant metastasis who underwent PBT at our institution between 2006 and 2021. To evaluate the dosimetric advantages of PBT, comparative treatment plans using VMAT were created. Result: Six patients with pathologically diagnosed SNEC without distant metastasis were treated with PBT. Multimodal treatment was applied in five patients, including chemotherapy in four cases and surgery in two cases. The median follow-up period was 37.4 months (range: 6.9 to 108.9 months). At the end of the follow-up, three patients were alive without recurrence, while three had died due to the disease. Recurrence occurred in three cases: one local recurrence, one in cervical lymph nodes, and two distant metastases. A late adverse event of Grade 4 vision decrease was observed in one patient on the ipsilateral side. Compared with VMAT, PBT lowered the average brain dose (median 3.3 Gy (RBE) vs. 12.6 Gy), brainstem D2 cc (10.7 Gy (RBE) vs. 34.9 Gy) and contralateral optic nerve D0.1 cc (47.6 Gy (RBE) vs. 63.3 Gy), while doses to the ipsilateral optic pathway were comparable. Conclusions: PBT in multimodal treatment achieved feasible local control for SNEC. The dose-sparing effect of PBT was more evident in organs distant from the target, although careful consideration is required for adjacent structures.