Radiation Therapy of Brain-Stem Tumors

TUMORS OF the brain stem reportedly (1, 5) are seen most frequently in young children. In untreated cases, the disease usually progresses rapidly from the first symptom to death, although in some instances the natural history may be more indolent. These tumors are quite rare, always unresectable, and usually not amenable to biopsy. Such factors tend to limit the radiotherapist's experience and to make the results of his treatment difficult to evaluate. With the above facts in mind, it was thought worthwhile to review the Mayo Clinic experience with radiation treatment for this condition. Materials And Methods Evaluation was made in a retrospective fashion of patients whose diagnosis was established on a clinical basis only, on the basis of a diagnostic radiographic procedure (fractional pneumoencephalogram, angiogram, or Pantopaque rhombencephalogram), or on the basis of surgical observation of the tumor with or without biopsy confirmation. Radiation therapy was given for 677 of 1,772 patients having clinical or proved brain tumor from January 1955 through December 1967. The 61 patients with a diagnosis of brain-stem tumor studied for this report were among those 677. A patient was considered to have tumor of the brain stem if the tumor occupied any portion of the region posterior to the cerebral peduncles, ventral to the floor of the fourth ventricle, and rostral to the junction of the medulla oblongata with the spinal cord. This comprises the anatomic pons and medulla. Cerebellar tumors and tumors of the midbrain, ventricular system, cerebellopontine angles, and roof of the fourth ventricle were not considered in this study. Clinical Features Of the 61 patients, 27 (44 per cent) were thirteen years of age or younger at the time of onset of symptoms (TABLE I); 3 patients were two years old. Males outnumbered females 37 to 24. The majority of patients sought medical treatment within the first year after the onset of symptoms; 11 (18 per cent), however, had had difficulty for three years or longer, with 1 patient dating the onset nine years before treatment. Young patients were seen earlier in the course of the disease, since their presenting complaints were usually of a significant disturbance-such as ataxia. A large variety of symptomatology was demonstrated. Cranial nerve nuclei were involved frequently, the sixth and seventh nerves being affected most commonly at the time of initial examination (TABLE II). Increased intracranial pressure did not characterize these tumors until late, if at all. Only 2 patients, both under the age of ten years, presented with symptoms of increased intracranial pressure. Comment: Lesions expanding the brain stem usually become clinically evident quite early because the motor and sensory pathways, as well as the cranial nerve nuclei.