Time to administration of stereotactic radiosurgery to the cavity after surgery for brain metastases: a real-world analysis

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.

Preoperative stereotactic radiosurgery as neoadjuvant therapy for resectable brain tumors

PURPOSE

Stereotactic radiosurgery (SRS) is a method of delivering conformal radiation, which allows minimal radiation damage to surrounding healthy tissues. Adjuvant radiation therapy has been shown to improve local control in a variety of intracranial neoplasms, such as brain metastases, gliomas, and benign tumors (i.e., meningioma, vestibular schwannoma, etc.). For brain metastases, adjuvant SRS specifically has demonstrated positive oncologic outcomes as well as preserving cognitive function when compared to conventional whole brain radiation therapy. However, as compared with neoadjuvant SRS, larger post-operative volumes and greater target volume uncertainty may come with an increased risk of local failure and treatment-related complications, such as radiation necrosis. In addition to its role in brain metastases, neoadjuvant SRS for high grade gliomas may enable dose escalation and increase immunogenic effects and serve a purpose in benign tumors for which one cannot achieve a gross total resection (GTR). Finally, although neoadjuvant SRS has historically been delivered with photon therapy, there are high LET radiation modalities such as carbon-ion therapy which may allow radiation damage to tissue and should be further studied if done in the neoadjuvant setting. In this review we discuss the evolving role of neoadjuvant radiosurgery in the treatment for brain metastases, gliomas, and benign etiologies. We also offer perspective on the evolving role of high LET radiation such as carbon-ion therapy.

METHODS

PubMed was systemically reviewed using the search terms "neoadjuvant radiosurgery", "brain metastasis", and "glioma". ' Clinicaltrials.gov ' was also reviewed to include ongoing phase III trials.

RESULTS

This comprehensive review describes the evolving role for neoadjuvant SRS in the treatment for brain metastases, gliomas, and benign etiologies. We also discuss the potential role for high LET radiation in this setting such as carbon-ion radiotherapy.

CONCLUSION

Early clinical data is very promising for neoadjuvant SRS in the setting of brain metastases. There are three ongoing phase III trials that will be more definitive in evaluating the potential benefits. While there is less data available for neoadjuvant SRS for gliomas, there remains a potential role, particularly to enable dose escalation and increase immunogenic effects.

GammaTile® (GT) as a brachytherapy platform for rapidly growing brain metastasis

Background

A subset of brain metastasis (BM) shows rapid recurrence post-initial resection or aggressive tumor growth between interval scans. Here we provide a pilot experience in the treatment of these BM with GammaTile® (GT), a collagen tile-embedded Cesium 131 (¹³¹Cs) brachytherapy platform.

Methods

We identified ten consecutive patients (2019-2023) with BM that showed either (1) symptomatic recurrence while awaiting post-resection radiosurgery or (2) enlarged by >25% of tumor volume on serial imaging and underwent surgical resection followed by GT placement. Procedural complication, 30-day readmission, local control, and overall survival were assessed.

Results

For this cohort of ten BM patients, 3 patients suffered tumor progression while awaiting radiosurgery and 7 showed >25% tumor growth prior to surgery and GT placement. There were no procedural complications or 30-day mortality. All patients were discharged home, with a median hospital stay of 2 days (range: 1-9 days). 4/10 patients experienced symptomatic improvement while the remaining patients showed stable neurologic conditions. With a median follow-up of 186 days (6.2 months, range: 69-452 days), no local recurrence was detected. The median overall survival (mOS) for the newly diagnosed BM was 265 days from the time of GT placement. No patients suffered from adverse radiation effects.

Conclusion

Our pilot experience suggests that GT offers favorable local control and safety profile in patients suffering from brain metastases that exhibit aggressive growth patterns and support the future investigation of this treatment paradigm.

Neoadjuvant stereotactic radiosurgery for brain metastases: a new paradigm

OBJECTIVE

For patients with surgically accessible solitary metastases or oligometastatic disease, treatment often involves resection followed by postoperative stereotactic radiosurgery (SRS). This strategy has several potential drawbacks, including irregular target delineation for SRS and potential tumor "seeding" away from the resection cavity during surgery. A neoadjuvant (preoperative) approach to radiation therapy avoids these limitations and offers improved patient convenience. This study assessed the efficacy of neoadjuvant SRS as a new treatment paradigm for patients with brain metastases.

METHODS

A retrospective review was performed at a single institution to identify patients who had undergone neoadjuvant SRS (specifically, Gamma Knife radiosurgery) followed by resection of a brain metastasis. Kaplan-Meier survival and log-rank analyses were used to evaluate risks of progression and death. Assessments were made of local recurrence and leptomeningeal spread. Additionally, an analysis of the contemporary literature of postoperative and neoadjuvant SRS for metastatic disease was performed.

RESULTS

Twenty-four patients who had undergone neoadjuvant SRS followed by resection of a brain metastasis were identified in the single-institution cohort. The median age was 64 years (range 32-84 years), and the median follow-up time was 16.5 months (range 1 month to 5.7 years). The median radiation dose was 17 Gy prescribed to the 50% isodose. Rates of local disease control were 100% at 6 months, 87.6% at 12 months, and 73.5% at 24 months. In 4 patients who had local treatment failure, salvage therapy included repeat resection, laser interstitial thermal therapy, or repeat SRS. One hundred thirty patients (including the current cohort) were identified in the literature who had been treated with neoadjuvant SRS prior to resection. Overall rates of local control at 1 year after neoadjuvant SRS treatment ranged from 49% to 91%, and rates of leptomeningeal dissemination from 0% to 16%. In comparison, rates of local control 1 year after postoperative SRS ranged from 27% to 91%, with 7% to 28% developing leptomeningeal disease.

CONCLUSIONS

Neoadjuvant SRS for the treatment of brain metastases is a novel approach that mitigates the shortcomings of postoperative SRS. While additional prospective studies are needed, the current study of 130 patients including the summary of 106 previously published cases supports the safety and potential efficacy of preoperative SRS with potential for improved outcomes compared with postoperative SRS.

Preoperative stereotactic radiosurgery in the management of brain metastases and gliomas

Stereotactic radiosurgery (SRS) is the delivery of a high dose ionizing radiation in a highly conformal manner, which allows for significant sparing of nearby healthy tissues. It is typically delivered in 1-5 sessions and has demonstrated safety and efficacy across multiple intracranial neoplasms and functional disorders. In the setting of brain metastases, postoperative and definitive SRS has demonstrated favorable rates of tumor control and improved cognitive preservation compared to conventional whole brain radiation therapy. However, the risk of local failure and treatment-related complications (e.g. radiation necrosis) markedly increases with larger postoperative treatment volumes. Additionally, the risk of leptomeningeal disease is significantly higher in patients treated with postoperative SRS. In the setting of high grade glioma, preclinical reports have suggested that preoperative SRS may enhance anti-tumor immunity as compared to postoperative radiotherapy. In addition to potentially permitting smaller target volumes, tissue analysis may permit characterization of DNA repair pathways and tumor microenvironment changes in response to SRS, which may be used to further tailor therapy and identify novel therapeutic targets. Building on the work from preoperative SRS for brain metastases and preclinical work for high grade gliomas, further exploration of this treatment paradigm in the latter is warranted. Presently, there are prospective early phase clinical trials underway investigating the role of preoperative SRS in the management of high grade gliomas. In the forthcoming sections, we review the biologic rationale for preoperative SRS, as well as pertinent preclinical and clinical data, including ongoing and planned prospective clinical trials.

Hypofractionated postoperative stereotactic radiotherapy for large resected brain metastases

PURPOSE

The aim of the present retrospective study was to report outcomes after hypofractionated stereotactic radiotherapy (HSRT) for resected brain metastases (BM).

PATIENTS AND METHODS

We reviewed results of patients with resected BM treated with postoperative HSRT (3×7.7Gy to the prescription isodose 70%) between May 2013 and June 2020. Local control (LC), distant brain control (DBC), overall survival (OS), leptomeningeal disease relapse (LMDR), and radiation necrosis (RN) occurrence were reported.

RESULTS

Twenty-two patients with 23 brain cavities were included. Karnofsky Performance status (KPS) was≥70 in 77.3%. Median preoperative diameter was 37mm [21.0-75.0] and median planning target volume (PTV) was 23 cm³ [9.9-61.6]. Median time from surgery to SRT was 69 days [7-101] and 48% of patients had a local relapse on pre-SRT imaging. Median follow-up was 17.5 months [1.6-95.9]. One and two-year LC rates were 60.9 and 52.2% respectively. One and 2-year DBC rates were 45.5 and 40.9%. Median OS was 16.5 months. Four patients (18.2%) presented LMDR during follow-up. RN occurred in 6 patients (27.2%). Three factors were associated with OS: ECOG-PS (P=0.009), KPS (P=0.04), and cystic metastasis before surgery (P=0.037). Several factors were related to RN occurrence: PTV diameter and volume, Normal brain V21, V21 and V24 isodoses volumes.

CONCLUSION

HSRT is the most widely used scheme for larger brain cavities after surgery. The optimal dose and scheme remain to be defined as well as the optimal delay between postoperative SRT and surgery. Dose escalation may be necessary, especially in case of subtotal resection.

Treatment of breast cancer brain metastases: radiotherapy and emerging preclinical approaches

The breast is one of the common primary sites of brain metastases (BM). Radiotherapy for BM from breast cancer may include whole brain radiation therapy (WBRT), stereotactic radiosurgery (SRS), and stereotactic radiotherapy (SRT), but a consensus is difficult to reach because of the wide and varied protocols, indications, and outcomes of these interventions. Overall, dissemination of disease, patient functional status, and tumor size are all important factors in the decision of treatment with WBRT or SRS. Thus far, previous studies indicate that WBRT can improve tumor control compared to SRS, but increase side effects, however no randomized trials have compared the efficacy of these therapies in BM from breast cancer. Therapies targeting long non-coding RNAs and transcription factors, such as MALAT1, HOTAIR, lnc-BM, TGL1, and ATF3, have the potential to both prevent metastatic spread and treat BM with improved radiosensitivity. Given the propensity for HER2+ breast cancer to develop BM, the above-mentioned cell lines may represent an important target for future investigations, and the development of everolimus and pyrotinib are equally important.