Abstract

We sought to determine the maximum tolerated dose (MTD) of 5-fraction stereotactic radiosurgery (SRS) with 5-mm margins delivered with concurrent temozolomide in newly diagnosed glioblastoma.We enrolled adult patients with newly diagnosed glioblastoma to 5 days of SRS in a 3+3 design on 4 escalating dose levels: 25, 30, 35, and 40 Gy. Dose limiting toxicity (DLT) was defined as CTCAE Grade 3-5 acute or late CNS toxicity, including adverse radiation effect (ARE), the imaging correlate of radiation necrosis.From 2010 to 2015, 30 patients were enrolled. The median age was 66 years (range 51-86 years). The median target volume was 60 cm3 (range 14.7-137.3 cm3). DLT occurred in 2 patients: one for post-treatment cerebral edema and progressive disease at 3 weeks (Grade 4, Dose 40 Gy); another patient died 1.5 weeks following SRS from post-operative complications (Grade 5, Dose 40 Gy). Late grade 1-2 ARE occurred in 8 patients at a median of 7.6 months (range 3.2-12.6 months). No grade 3-5 ARE occurred. With a median follow-up of 13.8 months (range 1.7-64.4 months), the median survival times were: PFS 8.2 months (95%CI 4.6-10.5), OS 14.8 months (95%CI 10.9-19.9), MGMT hypermethylated 19.9 months (95%CI 10.5-33.5) vs. 11.3 months (95%CI 8.9-17.6) for no/unknown hypermethylation (p=0.03), and 27.2 months (95%CI 11.2-48.3) if late ARE occurred vs. 11.7 months (95%CI 8.9-17.6) for no ARE (p=0.08).The per-protocol MTD of 5-fraction SRS with 5-mm margins with concurrent temozolomide was 40 Gy in 5 fractions. ARE was limited to grade 1-2 and did not statistically impact survival.

View details for DOI 10.1093/neuonc/noaa019

View details for PubMedID 32002547