• Sibo Tian, Lisa J Sudmeier, Chao Zhang, Nicholas A Madden, Zachary S Buchwald, Hui-Kuo G Shu, Walter J Curran, Bree R Eaton, and Natia Esiashvili.
• Department of Radiation Oncology, Winship Cancer Institute, Emory University, Atlanta, Georgia.
• Pediatr Blood Cancer. 2020 Jan 1; 67 (1): e28027.

BackgroundRadiotherapy boost to the entire posterior fossa (PF) is standard of care for high-risk (H-R) medulloblastoma patients; the utility of tumor bed (TB)-only boost is unclear. The purpose of this study was to examine the impact of PF versus TB boost volume on tumor control and survival in the H-R medulloblastoma population.MethodsSingle-institution records for patients with H-R medulloblastoma were reviewed. The median craniospinal irradiation dose was 36 Gy (range, 23.4-45 Gy), and boost doses to either PF or TB were 54 to 55.8 Gy. PF (local) failures were scored as in-field, marginal (between 80% and 95% isodose lines), or distant. Kaplan-Meier methods and Cox proportional hazards were used to assess the impact of radiation boost technique on local control (LC) and survival endpoints.ResultsThirty-two patients with H-R medulloblastoma were treated between 1990 and 2015, with a median follow-up length of 5.12 years. Twenty-two patients received PF boost, and 10 received TB boost. Patient and disease characteristic were comparable between groups. A total of 11 PF failures occurred, including 3 isolated LFs (2 in the PF and 1 in the TB group). Most PF failures were in-field: three of four in the TB group and six of seven in the PF group; the remainder were marginal failures. TB boost was not associated with inferior LC (hazard ratio [HR] 0.86, log-rank P = 0.81) or overall survival (HR 1.40, P = 0.56) compared with PF boost.ConclusionReduced-volume radiotherapy boost to the TB does not appear to compromise LC or survival in patients with H-R medulloblastoma; it may reduce the risk of ototoxicity.© 2019 Wiley Periodicals, Inc.

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