Extended field stereotactic radiosurgery for recurrent glioblastoma

Background: Stereotactic radiosurgery (SRS) is among the few therapeutic options for glioblastoma that recurs after standard radiation and chemotherapy, but its efficacy has been limited. Methods: Since November 2007, the authors have modified the clinical target volume by adding a 0.5- to 1-cm margin to the gadolinium-enhanced area (extended field SRS), in contrast to conventional SRS using no margin to set the clinical target volume. A total of 35 recurred glioblastoma lesions in 9 patients were treated with conventional SRS between December 1990 and January 2007, and 14 lesions in 9 patients were treated with extended field SRS. Results: The median follow-up periods were 7 months (range, 3-29 months) and 8 months (range, 6-27 months), respectively. The local control rate was 47% for conventional SRS and 93% for extended field SRS (P =.0035), and the numbers of radiation necrosis observed in SRS-treated lesions were 2 and 4, respectively. The median overall survival from the diagnosis was 24 months (range, 14-57 months) for conventional SRS and 21 months (range, 15-51 months) for extended field SRS (statistically not significant). Seven patients treated with conventional SRS died during follow-up, 6 from progression of the SRS-treated tumor, whereas 7 patients treated with extended field SRS died during follow-up, 6 from remote intracerebral dissemination. Conclusions: Extended field SRS was superior to conventional SRS in the local control of small recurrent lesions of glioblastoma, although a further device to suppress remote dissemination may be necessary to increase survival.