Pulsed Reduced Dose Rate Reirradiation for Recurrent Primary Central Nervous System Tumors

Results: For the entire cohort, the 5-year local control (LC) was 69.6% (95% CI 50e89.2%), and overall survival (OS) was 81.4% (95% CI 65.3e97.5%). All tumor failures were in-field and no distant metastases have yet been observed. In multivariate analysis, LC was significantly associated with prescribed RT dose (HR 0.78 per Gy, pZ0.022) and GTV at RT (HR 1.03 per cm, pZ0.018), while OS was significantly associated with D1cm (HR 0.89 per Gy, pZ0.038). Comparing radiation plans by cohort, the median D1cm in patients experiencing failure was 66.75 Gy (RBE) compared to a median of 76.25 Gy (RBE) in those remaining controlled (pZ0.017). Among the 14 patients with a D1cm 67 Gy (RBE) had a median follow-up of 43 months. The 5-year LC in this subset was 81.1% (95% CI 61.7e100%) (pZ0.004 overall comparison by GTV 67 Gy (RBE)). To improve outcomes, multidisciplinary efforts should focus on optimizing tumor resection to facilitate adequate GTV coverage. Author Disclosure: M.W. McDonald: None. O.R. Linton: Research Grant; Jesse N. Jones, III Memorial Fund.