Patterns of imaging failures in glioblastoma patients treated with chemoradiation: a retrospective study

Glioblastoma multiforme (GBM) is the most common primary brain tumor of adults and carries a poor prognosis. This study sought to investigate recurrence patterns of GBM treated with temozolomide-based chemoradiation. Records for 31 patients treated for newly diagnosed GBM between 2007 and 2009 were retrospectively analyzed. Ten patients received maximal surgical resection followed by conventionally fractionated radiation (CFR) to a median dose of 60 Gy with concurrent and planned adjuvant temozolomide. Twelve patients were treated with maximal surgical debulking, intracavitary brachytherapy (ICB), and external beam radiation therapy with concurrent and planned adjuvant temozolomide. The remaining 9 patients had unresectable disease and underwent biopsy followed by a hypofractionated course of radiation to a median dose of 60 Gy over 10 fractions. Tumor failure was classified as local, marginal, or distant according to whether the recurrence was completely inside, crossed, or completely outside the 100% isodose line. With a median follow-up of 12.6 months, 5 patients were lost to follow-up, while the remaining 26 patients (100%) developed recurrent disease. The first failures totaled 29 discrete lesions, of which 15 (52%), 6 (21%), and 8 (28%) were local, marginal, and distant failures at median times of 6.8, 10.1, and 7.9 months, respectively. Marginal or distant failure was more likely in ICB patients as compared to CFR patients. While local failure predominated, distant failures were not uncommon, particularly at later time points. As local control of GBM improves, further study is needed to identify and appropriately treat patients susceptible to distant failure.