Radiation Therapy in the Treatment of Cerebral Astrocytoma

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Abstract
With the advent of more sensitive diagnostic techniques, we are encountering an increasing number of young patients harboring cerebral astrocytoma. The great danger in such patients is that the astrocytoma cells will undergo dedifferentiation to a higher state of malignancy. An essential question is whether the use of postoperative adjuvant radiation therapy can decrease the incidence of this event. Because a prospective, randomized study has never been carried out, it is extremely difficult to ascertain whether radiation therapy should be given to these patients. This article reviews the main retrospective clinical studies in an attempt to determine whether the addition of radiation therapy increases the length or quality of survival in patients with astrocytoma. Based on this literature review, the following tentative conclusions have been reached: (a) All reported studies are inconclusive; therefore, dogmatic statements as to whether radiation therapy should be used are not warranted. (b) One should try to obtain pathological confirmation of the precise nature of all tumor-like cerebral lesions that have been detected on neuroradiological studies. (c) Consistent with sound neurosurgical judgment, every attempt should be made to carry out a gross total removal of the hemispheric astrocytoma. (d) In the case of such a gross total surgical removal and even in its absence in the case of a juvenile pilocytic astrocytoma, radiation therapy may be withheld and the patient carefully followed for tumor recurrence. (e) In those cases where total removal cannot be accomplished, postoperative radiation therapy seems warranted. (f) Such radiation therapy should be given in a conventional fractionated schedule to a maximum of 5500 rads. The radiation therapy should not be given to the whole brain, but rather to the tumor plus a limited surrounding margin as determined by computed tomography/magnetic resonance imaging. Such a treatment regimen may reasonably be expected to lead to a 5-year survival rate of approximately 40%.

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