Intraoperative radiotherapy (IORT)—a resurrected option for treating glioblastoma?

Despite surgical resection, radiochemotherapy and adjuvant chemotherapy, glioblastoma multiforme (GBM) is still associated with an extremely poor prognosis. As almost all tumors recur locally and evidence for a radiation dose-dependent effect on survival exists, intraoperative radiotherapy (IORT) could be an approach to avoid tumor cell proliferation between surgery and radiochemotherapy while sparing healthy tissue. The majority of previous studies used forward-scattering electron tubes (resembling intraoperative electron radiotherapy, IOERT) and suffered from technical and geometrical limitations. Consequently, the outcomes in previous studies range from highly beneficial to merely effective. This review shall give an overview on past, present and future applications of IORT for GBM and shall discuss what prospective steps are to be taken to thoroughly assess whether the approach has the ability to prolong patient survival.