2057 A phase [formula omitted] study of fractionated intensity modulated radiation therapy in the treatment of patients with primary or recurrent high grade gliomas

Abstract

‘Department of Radiation Oncology,and lDepartment of Neurosurgery, New England Medical Center, Tufts University School of Medicine, Boston, Massachusetts. ‘Baystate Medical Center, Springfield, Massachusetts. Pumose To determine the safety and effectiveness of fractionated intensity modulated radiation therapy (IMRT) in the treatment of primary and recurrent high grade gliomas Materials and Methods: Beginning in 1995, two prospective trials were undertaken at our institution to 1.) assess the potential role of dose escalation using hypofractionated IMRT for primary high grade gliomas, and 2.) re-irradiation using IMRT for recurrent high grade gliomas. Dosimetry and radiobiologic fractionation schemes for IMRT were designed for implant and stereotactic radiosurgery (SRS) ineligible patients to emulate V temporary interstitial implant (50 Gy @ .60 Gylhr) or single fraction radiosurgery of 15-20 Gy. Sixteen patients ( 14 Glioblastoma Multiforme (GBMI, 1 Anaplastic Astrocytoma (AA), 1 High grade Oligoastrocytoma) with a median age of 52 years (range 9-70 years1 have been treated on these protocols. Eight patients were treated for primary brain lesions, while the remaining 8 had recurrent disease after previous high dose conventional radiation therapy (median dose 5940 cGy). All patients had a Karnofsky Performance Status (KPS) of > 60. Patients were seen in follow-up two weeks after completion of therapy, then every 4 to 8 weeks. CT or MRI scans were performed at 6 to 8 weeks, then every 2-3 months. Cases were analyzed with regard to survival, acute toxicities, and corticosteroid use. Results: The median follow-up of the 16 patients was 5 months (range 2-8 months). Patients were treated with a median prescribed dose of 3325 cGy (range 1600-3500) using 400-500 cGy per fraction. The median tumor volume was 27.93 cc (range 10-l 19 cc). At last follow-up, 9 (56%) patients were alive. Of the patients who received a primary boost with IMRT, one patient at 7 months has no evidence of disease by CT/MRI while the remaining patients have persistent abnormalities. All patients who have been retreated for recurrence have persistent radiographic abnormalities on CT/MRI which could correspond to either radionecrosis or residual tumor. There were no acute toxicities or worsening of symptoms associated with the treatment. Of 10 evaluable patients,4 (40%) were steroid dependent at last follow-up. Conclusion; Hypofractionated IMRT is a feasible alternative with no appreciable short term toxicity to SRSlinterstitial brachytherapy ineligible patients for boost es part of primary treatment, or in the treatment of recurrent high grade gliomas. High dose fractionated treatment with IMRT may be most suitable for patients with highly irregular or large target volumes and/or are located in critically sensitive areas.