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Background The main complication after hypofractionated radiotherapy for lung carcinoma is radiation-induced lung toxicity, which can be divided into radiation pneumonitis (acute toxicity, occurring within 6 months) and lung fibrosis (late toxicity, occurring after 6 months). The literature describes several predictive factors related to the patient, to the tumor (volume, central location), to the dosimetry and to biological factors. Materials and methods This study is a retrospective analysis of 90 patients treated with stereotactic body irradiation for stage I non-small-cell lung carcinoma between December 2010 and May 2015. Results Radiation pneumonitis was observed in 61.5% of the patients who were mainly asymptomatic (34%). Chronic obstructive pulmonary disease was not predictive of radiation pneumonitis, whereas active smoking was protective. Centrally located tumors were not more likely to result in this complication if the radiation schedule utilized adapted fractionation. In our study, no predictive factor was identified. Whereas the mean lung dose was a predictive factor in 3D radiotherapy, the lung volume irradiated at high doses seemed to be involved in the pathogenesis after hypofractionated radiotherapy. Conclusion The discovery of predictive factors for radiation pneumonitis is difficult due to the rarity of this complication, especially with an 8 × 7.5 Gy schedule. Radiation pneumonitis seems to be correlated with the volume irradiated at high doses, which is in contrast to the known knowledge about the organs in parallel. This finding leads us to raise the hypothesis that vessel damage, organs in series, occurring during hypofractionated radiotherapy could be responsible for this toxicity.

International audience; Purpose: The purpose of this prospective dosimetric study was to assess the dose distribution regarding the brain areas implied in cognitive functions using two approaches: volumetric modulated arc therapy (VMAT) and helical tomotherapy (HT).Patients and methods: Thirty-seven patients were treated using a dual-arc VMAT approach for supratentorial glioblastoma between 2016 and 2018. The total dose of 60 Gy in 30 daily fractions was administered to the planning target volume (PTV). The brain structures that play an important role in cognitive physiology, such as the hippocampi, corpus callosum, cerebellum, subventricular zones (SVZ), were delineated. For each patient, a new treatment plan in HT was determined by a second medical physicist in a blindly fashion according to the same dose constraints and priorities. Statistical analyses were performed using the Wilcoxon-signed rank test.Results: Conformity indexes remained similar with both techniques. The mean values were 0.96 (0.19–1.00) for VMAT and 0.98 (range, 0.84–1.00) for HT, respectively (P = 0.73). Significant D50% reductions were observed with VMAT compared to HT: 14.6 Gy (3.8–28.0) versus 17.4 Gy (12.1–25.0) for the normal brain (P = 0.014); 32.5 Gy (10.3–60.0) versus 35.6 Gy (17.1–58.0) for the corpus callosum (P = 0.038); 8.1 Gy (0.4–34.0) versus 12.8 Gy (0.8–27.0) for the cerebellum (P < 0.001), respectively.Conclusion: The VMAT approach seemed to improve the sparing of the key brain areas implied in cognitive functions without jeopardizing PTV coverage.; Objectif: L’objectif de cette étude prospective dosimétrique était d’évaluer la distribution de dose en regard des aires cérébrales impliquées dans les fonctions cognitives selon deux techniques : arcthérapie volumétrique modulée (VMAT) et tomothérapie hélicoïdale (HT).Patients et méthodes: Trente-sept patients ont été pris en charge pour un glioblastome sus-tentoriel par une VMAT à base de deux arcs entre 2016 et 2018. Une dose totale de 60 Gy en 30 fractions quotidiennes a été administrée au volume cible prévisionnel (PTV). Les structures cérébrales occupant une place importante dans la physiologie cognitive, comme les hippocampes, le corps calleux, le cervelet, les zones péri-ventriculaires (ZPV), ont été délinées. Pour chaque patient, un nouveau plan de HT a été déterminé en aveugle par une seconde physicienne médicale selon les mêmes contraintes de dose et priorités. Les analyses statistiques ont été menées à l’aide du test des rangs signés de Wilcoxon.Résultats: Les indices de conformité étaient similaires entre les deux techniques. Les valeurs moyennes étaient de 0,96 (0,19–1,00) respectivement en VMAT et de 0,98 (0,84–1,00) en tomothérapie hélicoïdale (p = 0,73). Des réductions significatives de la D50 % (dose reçue dans 50 % du volume) ont été observées en VMAT, comparativement à la HT : respectivement 14,6 Gy (3,8–28,0) contre 17,4 Gy (12,1–25,0) pour l’encéphale sain (p = 0,014), 32,5 Gy (10,3–60,0) contre 35,6 Gy (17,1–58,0) pour le corps calleux (p = 0,038), 8,1 Gy (0,4–34,0) contre 12,8 Gy (0,8–27,0) pour le cervelet (p < 0,001).Conclusion: La VMAT semblait améliorer la protection des principales régions cérébrales impliquées dans les fonctions cognitives sans compromettre la couverture du PTV.