A phase II trial of accelerated radiotherapy using weekly stereotactic conformal boosts for supratentorial glioblastoma multiforme. RTOG-0023.

1511 Background: Malignant gliomas undergo molecular changes during radiation therapy (RT) that lead to accelerated proliferation. This phase II trial was performed to assess the feasibility, toxicity, and efficacy of dose-intense RT employing weekly fractionated stereotactic radiotherapy (FSRT) boosts for patients with glioblastoma multiforme (GBM).,Patients with histologically confirmed GBM with postoperative enhancing tumor plus tumor cavity diameter ≤ 60 mm were enrolled. 50 Gy of standard RT was given in daily 2 Gy fractions. In addition, patients received four FSRT treatments, once weekly, during weeks 3-6 in lieu of standard RT to the postoperative tumor bed plus enhancing tumor plus 5 mm (PTV). FSRT dosing of either 7 Gy (PTV≤40 mm) or 5 Gy (PTV>40 mm) per fraction was given for a cumulative dose of 70 or 78 Gy in 29 (25 standard RT + 4 FSRT) treatments over 6 weeks. A relocatable frame and shaped conformal fields were used for FSRT. Following the RT course, BCNU at 80 mg/m was given for 3 days, q 8 weeks, for 6 cycles. The sample size was calculated to compare survival with RTOG-RPA class using one-sided p-values and calculated hazard ratios.,76 patients were analyzed. Significant RT toxicity included: one grade 4 acute (lethargy) and one grade 3 late (necrosis). The median survival time (MST) was 12.5 months. No survival difference is seen compared to the RTOG historical database. Matched pair cox regression also showed no significant survival difference. For RPA class IV patients (50% of total) the MST was 14.7 mos. compared to 11.3 mos. for historic controls (p=0.15). Patients with gross total resection (41%) had a MST of 16.1 mos. vs. 12.0 mos. for historic controls (p=0.19). RT quality control was favorable with 90% compliance.,This initial RTOG trial employing FSRT was feasible and well tolerated. There appears to be no significant survival benefit for GBM patients using this dose-intense, accelerated RT regimen although RPA class IV and gross total resection patients trended toward improved outcome. No significant financial relationships to disclose.