Seed migration to the spinal canal after postresection brachytherapy to treat a large brain metastasis

Seed migration after interstitial prostate brachytherapy has been well documented in the literature. However, there have been no detailed reports of seed migration after permanent interstitial brachytherapy to treat cerebral malignancies. In this article, the authors report a rare case of seed migration after adjuvant cesium-131 ((131)Cs) brachytherapy was used to treat a large paraventricular brain metastasis.

The patient was a 63-year-old man with a 5.8-cm right frontal metastasis abutting the right lateral ventricle and causing severe edema and mass effect. The patient was enrolled in an ongoing clinical trial at our institution to receive permanent intraoperative (131)Cs brachytherapy in an effort to prevent tumor recurrence in the resection cavity. Stranded seeds were covered with Surgicel, and the cavity was filled with Tisseel to prevent seed migration.

Imaging obtained at 54 days postsurgery showed no seed migration, but imaging obtained at 158 days revealed 12 brachytherapy seeds in the spinal canal from T11 to S2. The seeds were left in place because they were inactive at this time due to the short half-life of (131)Cs (9.7 days); they remained stable on followup imaging, and the patient was asymptomatic.

Although the clinical consequences remain unclear, the migration of inactive seeds is not currently considered to be a complication of intracerebral brachytherapy and we do not believe that additional measures must be taken to prevent it.