biostudies-literatureUnknown56von der Grun JVarian Medical Systems Inc<h4>Background</h4>The FLASH effect is considered being the widening of the therapeutic window at (ultra-)high dose rates due to sparing of normal tissues while preserving tumor response. Our goal was to provide first data on the safety in treating a patient using a conventional linear accelerator converted to deliver 9 MeV UHDR electron beams in the research setting.<h4>Material & methods</h4>A conventional Varian TrueBeam linac was converted in the research setting to become capable of delivering 9 MeV UHDR electron beams. A phase I trial protocol was approved by the local authorities (NCT06549439). One patient with ≥ 1 melanoma (sub)-cutaneous lesion(s) was treated with 3x 9 Gy. The first two fractions were applied via e-Flash and the third via conventional electrons.<h4>Results</h4>HerClinical and translational radiation oncology101047https://www.ebi.ac.uk/biostudies/studies/S-EPMC12509727biostudies-literatureFirst-in-human e-Flash radiotherapy using a modified conventional C-arm linear accelerator.PMC12509727Balermpas PPsoroulas SGuckenberger MSharma RAvon der Grun JMangana JFesslmeier DTirpak LSmith WVilalta MDal Bello RRamelyte ETanadini-Lang SKrayenbuehl JfalseFirst-in-human e-Flash radiotherapy using a modified conventional C-arm linear accelerator.<h4>Background</h4>The FLASH effect is considered being the widening of the therapeutic window at (ultra-)high dose rates due to sparing of normal tissues while preserving tumor response. Our goal was to provide first data on the safety in treating a patient using a conventional linear accelerator converted to deliver 9 MeV UHDR electron beams in the research setting.<h4>Material & methods</h4>A conventional Varian TrueBeam linac was converted in the research setting to become capable of delivering 9 MeV UHDR electron beams. A phase I trial protocol was approved by the local authorities (NCT06549439). One patient with ≥ 1 melanoma (sub)-cutaneous lesion(s) was treated with 3x 9 Gy. The first two fractions were applied via e-Flash and the third via conventional electrons.<h4>Results</h4>Her2026-01-01T00:00:00Z2026 Jan2026-07-15T07:47:21.205Z2026-07-01T03:07:58.645ZS-EPMC125097274108098910.1016/j.ctro.2025.101047