[Reirradiation: A new therapeutic paradigm in oncology]

Reirradiation (reRT) has become an essential therapeutic option for selected patients with locoregional recurrences, when surgery or systemic therapies alone provide limited benefit. Initially restricted to palliative intent, reRT is now increasingly delivered with curative aims, supported by major advances in imaging and radiation techniques such as IMRT, stereotactic body radiotherapy (SBRT), brachytherapy, and image-guided proton therapy. Although few randomized trials exist, they have provided meaningful insights across tumor sites: in glioblastoma, combining reRT with bevacizumab improves progression-free survival without an overall survival benefit; in postoperative head and neck cancers, reRT improves locoregional control but not survival; and in nasopharyngeal carcinoma, hyperfractionation reduces late toxicity and improves 3-year survival. Median survival varies by site, ranging from approximately 8 months in glioblastoma to over 16 months in favorable head and neck subgroups, reaching 2-year survival rates up to 60% in selected peripheral lung or prostate recurrences, and several years in breast cancer. Patient selection remains pivotal, based on performance status, interval since prior irradiation, organ function, and tumor volume. Future perspectives rely on technological innovations - including FLASH radiotherapy, minibeams, hadron therapy, nanoparticles, and artificial intelligence - alongside international standardization efforts (ESTRO, ReCOG, FReTREAT) and the development of robust dose-summation platforms. Together, these advances aim to expand indications while improving treatment safety and harmonization.