Extraneural metastatic glioblastoma after interstitial brachytherapy

This is a report of 3 cases of extraneural metastasis of glioblastoma after interstitial radiation and assessment of pertinent literature addressing concern over an increased risk of these events with this therapy.

In a series of 82 patients treated with (125)I brachytherapy for primary malignant brain tumors over a 7-year interval, 3 cases of extraneural glioblastoma were identified. The multicatheter technique for delivery of (125)I sources was utilized in all. Extraneural metastases were documented by imaging studies or biopsy. Over the same period, 310 patients with primary malignant brain tumors were treated without brachytherapy.

Biopsy-proven scalp and skull metastases occurred in 2 patients, at 3 and 8 months following brachytherapy. Each developed radiographic evidence of systemic metastases at 7 and 14 months postbrachytherapy, respectively. The third patient developed biopsy-proven cervical node involvement 4 months after brachytherapy. No patients with malignant gliomas undergoing craniotomy or stereotactic biopsy, but not brachytherapy, during the same time period developed extraneural metastases. Incidence in previously reported series commenting on this otherwise rare process range from 0% to 4.3%. The incidence of extraneural metastases in this series is 3.7% (3/82) and is comparable to those reports.

Percutaneous catheter-delivered brachytherapy may be associated with an increased incidence of extraneural metastatic glioma.