Jacob Shabason, Presenter: Nothing to Disclose

David Sutton MS, Abstract Co-Author: Nothing to Disclose

Robert A. Lustig MD, Abstract Co-Author: Nothing to Disclose

Christine Hill-Kayser, Abstract Co-Author: Nothing to Disclose

Purpose/Objectives: Despite aggressive multimodal therapy for pediatric glioblastoma multiforme (GBM), survival remains poor. Retrospective adult studies have shown that most GBMs recur within the high-dose radiation field. To our knowledge, no such studies have been performed in the pediatric population. As such, this study aims to evaluate the patterns of failure in pediatric patients with GBM after radiation therapy (RT).Materials/Methods: We conducted a retrospective review of 13 pediatric patients treated with RT for GBM from 2007-2013. Patients were treated with intensity-modulated radiation therapy (IMRT) or proton therapy, with treatment volumes defined using residual disease, surgical bed, edema, and 2 cm margin. First failure MRI scans were fused with treatment planning scans. Patterns of failure were defined as: in-field (≥ 95% of recurrence volume in the 95% isodose of the volume ≥ 45 Gy), marginal (≤ 95% of recurrence volume in the 95% isodose of the 45 Gy volume), or distant (recurrence outside of the RT field, ≤ 20% isodose line). Overall survival (OS) and progression free survival (PFS) were estimated using the Kaplan-Meir method calculated from the start of RT.Results: The patients had a mean age of 12.2 years (range 2-22) and were 53.8 % female. Seven patients (53.8%) underwent gross total resection (GTR), 5 (38.5%) had subtotal resection (STR), and 1 (7.7%) had a biopsy only. Twelve patients were treated with IMRT, and 1 was treated with proton therapy. Patients were treated to a mean total dose of 56.7 Gy (range 50.4 Gy-60 Gy), with dose reduced below 54 Gy for 2 patients who received prior radiation for other types of malignancies. Most patients (92.3%) were treated with concurrent chemotherapy: 10 with temozolomide, 1 with capecitabine, and 1 with temozolomide and bevacizumab. With a median follow up of 52.8 months, 9 patients (69.2%) developed recurrent disease. Of recurrences, 6 (66.7%) were in-field, 2 (22.2%) were marginal, and 1 (11.1%) was distant. Median OS and PFS were 18.2 months and 16.3 months, respectively.Conclusions: The majority of patients treated with adjuvant radiation fail in the region of high-dose RT, indicating the need for improvements in local therapy. These may include radiation dose escalation and novel radiosensitizing agents.

Shabason, J, Sutton, D, Lustig, R, Hill-Kayser, C, Patterns of Failure for Pediatric Glioblastoma Multiforme Following Radiation Therapy.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14042821.html