FLASH Radiotherapy for Skin Cancer

Inclusion Criteria: * Signed study Informed Consent Form * Karnofsky Performance Status (KPS) ≥ 60 * Age ≥ 60 years * Patients with histologically proven cSCC or patients with BCC either histologically proven or proven by non-invasive imaging: either Optical Coherence Tomography (OCT), Line-field OCT (LC-OCT) or Reflectance Confocal Microscopy (RCM) * Patients requiring radiotherapy treatment according to the dermato-oncology tumor board: patients who cannot undergo surgical procedure or patients who decline surgical resection, and/or anatomical locations where surgery can compromise function or cosmesis. * T1-T2 N0 lesions with a small (T1; lesion ≤ 2cm in diameter) or large (T2; 2cm \< lesion ≤ 4 cm) volume (TNM Classification of Malignant Tumours (TNM) Union for International Cancer Control (UICC), 8th Edition) * Lesions should be at least 4 cm apart if treated with 2 different modalities (including surgical treatment of lesions). Lesions should not be located on the face, except on the forehead, above a line situated 1 cm above the eyebrows. Lesions located on the scalp can be treated. Exclusion Criteria: * Previous radiotherapy in the treated area * Concomitant auto-immune disease with skin lesions * Concomitant use of radio-sensitizer drug * Cognitive disorders not compatible with the signature of informed consent or that may compromise compliance with the requirements of the study * Current, recent (within 10 days prior to start of study treatment), or planned parti…