Permanent low-activity¹²⁵I seed placement for the treatment of pediatric brain tumors: Preliminary experience

Although external beam radiation therapy is effective in the treatment of many pediatric brain neoplasms its use in this patient population has been associated with the development of significant cognitive and endocrine dysfunction and is severely limited as an option in previously irradiated patients. Therefore, we have adopted a strategy for management of residual microscopic disease by implantation of low-activity (125)I seeds in the tumor bed at the time of surgery. Six patients aged 2-14 years with recurrent tumors including two supratentorial primitive neuroectodermal tumors (n = 2), one medullo-blastoma, one malignant ependymoma (n = 1), glioblastoma (n = 1) and one pleomorphic xanthoastrocytoma were implanted at the time of reoperation. A total of 11-126 seeds were implanted resulting in total doses of 16-21.8 Gy (after theoretical infinite time) at a depth of 5 mm from the implanted resection bed. Five patients had prior external beam radiation while the other patient (2 years old at initial diagnosis) progressed after surgery and chemotherapy. Two patients had lasting local tumor control. One patient is alive at 390 weeks of follow-up and another who died of distant failure at 366 weeks had no recurrence on MRI at 333 weeks' follow-up. Only 2 patients had first local failures. These results suggest that the use of permanent low-activity ¹²⁵I seeds as an adjunct to surgery can provide good local tumor control and is a suitable treatment option for pediatric patients.