Patterns of recurrence of malignant astrocytoma following stereotactic interstitial brachytherapy with iodine-125 implants.

The pattern of tumor recurrence was studied in a series of 68 patients who were treated with interstitial brachytherapy for malignant astrocytoma. Thirty-six patients had newly diagnosed tumors and were treated following surgery and external beam therapy, while 32 were treated for recurrent tumors. Recurrence pattern was determined using computed tomography at the time of clinical deterioration. Thirty-eight percent of tumor recurrence occurred within the original tumor margin and 50% occurred at the original site but extended beyond the initial margin. In all, 88.0% recurred at the initial tumor site, 71.4% being confined to within 2 cm of the pretreatment tumor borders while 6.0% recurred intracranially outside of the initial tumor margin. One patient recurred with spinal metastasis while two patients developed systemic metastases. The significance of these findings is discussed.