Outcomes of Metastatic Brain Lesions Treated with Radioactive Cs-131 Seeds after Surgery: Experience from One Institution

Abstract

Introduction Brain metastases are common in patients with advanced systemic cancer and often recur despite treatment with surgical resection and radiotherapy. Whole brain radiation therapy (WBRT) and stereotactic radiosurgery (SRS) have significantly improved local control rates but are limited by complications including neurocognitive deficits and radiation necrosis. These risks can be higher in the re-irradiation setting. Brachytherapy may be an alternative method of additional targeted adjuvant radiotherapy with acceptable rates of toxicity. Methods A retrospective chart review of all patients undergoing resection for metastatic brain lesions and permanent low-dose rate Cs-131 brachytherapy was performed for one institution over a 10-year period. All patients had previous radiation therapy already and, after surgery, were followed with imaging every three months. Patient demographics, disease characteristics, intracranial disease, peri- and post-operative complications, and outcomes were recorded. The primary outcome of interest was local tumor recurrence at the site of brachytherapy while secondary outcomes included distant disease progression (within the brain) and complications such as radiation necrosis. Results During the study period, nine cases of individual patients met inclusion criteria. The median preoperative lesion diameter was 3 cm (0.8-4.1). The median overall survival after surgery and brachytherapy was 10.3 months, after excluding two patients who were lost to follow-up. Six of nine patients had no local recurrence, while three patients had development or progression of distant lesions. No patients experienced acute or delayed complications. Conclusion Cs-131 brachytherapy is a promising alternative method for controlling brain metastases after previous radiation interventions and surgical resection. In this case series, there were no incidences of local tumor recurrence or complications such as radiation necrosis.

Keywords: brachytherapy; brain metastases; local recurrence; local tumor control.

Figure 1. Series of images depicting preoperative, planning, and postoperative scans in a patient treated with Cs-131 brachytherapy. Preoperative T1 post-contrast magnetic resonance imaging (MRI) (A) depicts a 2.6 cm occipital lesion while post-operative T2 MRI dosimetry (B) shows the 60 Gy (purple) and 72 Gy (green) isodose lines overlayed on the planned target volume (orange). Post-operative computed tomography (CT) (C) confirmed seed placement with Leblanc dosimetry (D).