Pediatric brain stem tumors: patterns of treatment failure and their implications for radiotherapy.
There have been conflicting opinions regarding the correct volume to be used in radiotherapy fields for brain stem tumors of childhood. Whereas many clinicians recommend limited fields designed to cover the tumor volume with a margin, some have advocated whole brain radiotherapy. Using our clinical experience at Duke University Medical Center, we have made an attempt to determine the proper irradiation volume in this group of tumors. We have evaluated 38 patients with brain stem tumors in children less than 18 years of age. The most common presenting symptoms were headache, ataxia, and hemiparesis. Thirteen patients had a histologic diagnosis made prior to treatment or post-mortem. All had either an anaplastic astrocytoma or a glioblastoma multiforme. Tumors were located in the thalamus, hypothalamus, or midbrain in 9 patients and in the pons or medulla oblongata in the remaining 29 patients. All patients received a course of radiotherapy. The mean minimum tumor dose was 52.6 +/- 5 Gy given at 1.7 to 2.0 Gy/fraction. Twenty-three patients received radiation to a limited field and 14 received whole brain irradiation. In one patient, the field size could not be ascertained. The five year survival of the total group was 39%. The survival of patients with thalamic, hypothalamic, or midbrain tumors was 73% compared with 28% for those with tumors of the pons or medulla oblongata (p = 0.0159). Eighty-eight percent of the tumor recurrences in evaluable patients (22/25) occurred within the radiotherapy fields. Patients were stratified for tumor location and no difference was observed in survival or relapse-free survival among those individuals treated with limited irradiation fields or whole brain irradiation fields. When our results are examined in conjunction with previously published data, the bulk of existing evidence supports the use of limited fields for irradiation of brain stem tumors of childhood.
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