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

The role of GammaTile in the treatment of brain tumors: a technical and clinical overview

Malignant and benign brain tumors with a propensity to recur continue to be a clinical challenge despite decades-long efforts to develop systemic and more advanced local therapies. GammaTile (GT Medical Technologies Inc., Tempe AZ) has emerged as a novel brain brachytherapy device placed during surgery, which starts adjuvant radiotherapy immediately after resection. GammaTile received FDA clearance in 2018 for any recurrent brain tumor and expanded clearance in 2020 to include upfront use in any malignant brain tumor. More than 1,000 patients have been treated with GammaTile to date, and several publications have described technical aspects of the device, workflow, and clinical outcome data. Herein, we review the technical aspects of this brachytherapy treatment, including practical physics principles, discuss the available literature with an emphasis on clinical outcome data in the setting of brain metastases, glioblastoma, and meningioma, and provide an overview of the open and pending clinical trials that are further defining the efficacy and safety of GammaTile.

The role of cesium-131 brachytherapy in brain tumors: a scoping review of the literature and ongoing clinical trials

PURPOSE

Cesium-131 radioactive isotope has favored the resurgence of intracavitary brachytherapy in neuro-oncology, minimizing radiation-induced complications and maximizing logistical and clinical outcomes. We reviewed the literature on cesium-131 brachytherapy for brain tumors.

METHODS

PubMed, Web-of-Science, Scopus, Clinicaltrial.gov, and Cochrane were searched following the PRISMA extension for scoping reviews to include published studies and ongoing trials reporting cesium-131 brachytherapy for brain tumors.

RESULTS

We included 27 published studies comprising 279 patients with 293 lesions, and 3 ongoing trials. Most patients had brain metastases (63.1%), followed by high-grade gliomas (23.3%), of WHO Grade III (15.2%) and Grade IV (84.8%), and meningiomas (13.6%), mostly of WHO Grade II (62.8%) and Grade III (27.9%). Most brain metastases were newly diagnosed (72.3%), while most gliomas and meningiomas were recurrent (95.4% and 88.4%). Patients underwent gross-total (91.1%) or subtotal (8.9%) resection, with median postoperative cavity size of 3.5 cm (range 1-5.8 cm). A median of 20, 28, and 16 seeds were implanted in gliomas, meningiomas, and brain metastases, with median seed activity of 3.8 mCi (range 2.4-5 mCi). Median follow-up was 16.2 months (range 0.6-72 months). 1-year freedom from progression rates were local 94% (range 57-100%), regional 85.1% (range 55.6-93.8%), and distant 53.5% (range 26.3-67.4%). Post-treatment radiation necrosis, seizure, and surgical wound infection occurred in 3.4%, 4.7%, and 4.3% patients.

CONCLUSION

Initial data suggest that cesium-131 brachytherapy is safe and effective in primary or metastatic malignant brain tumors. Ongoing trials are evaluating long-term locoregional tumor control and future studies should analyze its role in multimodal systemic tumor management.

Surviving Over a Decade With Glioblastoma: A Clinical Course Characterized by Multiple Recurrences, Numerous Salvage Treatments, and Novel Use of Cesium-131 Tiles

The prognosis for patients diagnosed with recurrent glioblastoma (GBM) remains poor, with no clear standard of care regarding salvage therapy. Common approaches include chemotherapy, re-resection, tumor treating fields, and reirradiation. However, most studies have shown these to have limited benefits. Reirradiation is particularly difficult due to concern for increased risk of toxicity to surrounding normal brain tissue. A novel intracranial brachytherapy system called GammaTile® (GT Medical Technologies, Tempe, Arizona) involves the placement of Cesium-131 radioactive tiles in the tumor cavity following maximal safe resection. This allows for a highly conformal dose distribution with rapid fall-off to minimize overlap with prior radiation fields and for the application of radiation directly to the high-risk tumor bed. This case report highlights a patient with GBM who survived 11.5 years through multiple recurrences and discusses the many salvage treatments he received, including bevacizumab, irinotecan, and stereotactic radiosurgery (SRS). This case exemplifies that aggressive systemic and local therapies can work well in select patients allowing for long-term survival with a good quality of life. Further efforts should be made to identify which patients may benefit from these therapies. The case study additionally reports on the use of GammaTile therapy. Due to prior external beam radiation therapy and SRS to the treatment site, further external beam radiation options were limited, and the patient was offered GammaTile as local therapy. Although it did not provide a survival benefit in this case due to progressive disease outside of the field of treatment, GammaTile serves as a valuable option in providing local therapy to patients who can no longer receive further radiation. It should be used with careful consideration in lesions characterized by aggressive local invasion.

The Relationship Between Tumor Volume and Timing of Post-resection Stereotactic Radiosurgery to Maximize Local Control: A Critical Review

After maximally safe neurosurgical resection of brain metastases, stereotactic radiosurgery (SRS) is now recommended as an alternative to whole-brain radiation therapy (WBRT), which has been associated with cognitive decline. One complicating factor associated with SRS is that postoperative cavity dynamics can change dramatically, creating significant variability in the recommended timing of SRS. While SRS has been shown to improve local control (LC) in smaller tumor cavities, achieving excellent LC rates still remains a challenge in larger ones. Furthermore, factors predicting the optimal timing of SRS in relation to the cavity size need to be defined and implemented. Variables such as the delay between postoperative MRI and treatment are critical but poorly understood. One potential treatment option that may improve outcomes is brachytherapy, but the widespread implementation of this technique has been slow. This critical review analyzes the relationship between preoperative tumor volume, resection cavity size, and timing of SRS and explores how these variables must be understood in order to achieve the highest LC possible.