Phase I/II study of resection and intraoperative cesium-131 radioisotope brachytherapy in patients with newly diagnosed brain metastases

Brachytherapy in Brain Metastasis Treatment: A Scoping Review of Advances in Techniques and Clinical Outcomes

Brain metastases pose a significant therapeutic challenge in the field of oncology, necessitating treatments that effectively control disease progression while preserving neurological and cognitive functions. Among various interventions, brachytherapy, which involves the direct placement of radioactive sources into or near tumors or into the resected cavity, can play an important role in treatment. Current literature describes brachytherapy's capacity to deliver targeted, high-dose radiation while minimizing damage to adjacent healthy tissues-a crucial consideration in the choice of treatment modality. Furthermore, advancements in implantation techniques as well as in the development of different isotopes have expanded its efficacy and safety profile. This review delineates the contemporary applications of brachytherapy in managing brain metastases, examining its advantages, constraints, and associated clinical outcomes, and provides a comprehensive understanding of advances in the use of brachytherapy for brain metastasis treatment, with implications for improved patient outcomes and enhanced quality of life.

Response of treatment-naive brain metastases to stereotactic radiosurgery

With improvements in survival for patients with metastatic cancer, long-term local control of brain metastases has become an increasingly important clinical priority. While consensus guidelines recommend surgery followed by stereotactic radiosurgery (SRS) for lesions >3 cm, smaller lesions (≤3 cm) treated with SRS alone elicit variable responses. To determine factors influencing this variable response to SRS, we analyzed outcomes of brain metastases ≤3 cm diameter in patients with no prior systemic therapy treated with frame-based single-fraction SRS. Following SRS, 259 out of 1733 (15%) treated lesions demonstrated MRI findings concerning for local treatment failure (LTF), of which 202 /1733 (12%) demonstrated LTF and 54/1733 (3%) had an adverse radiation effect. Multivariate analysis demonstrated tumor size (>1.5 cm) and melanoma histology were associated with higher LTF rates. Our results demonstrate that brain metastases ≤3 cm are not uniformly responsive to SRS and suggest that prospective studies to evaluate the effect of SRS alone or in combination with surgery on brain metastases ≤3 cm matched by tumor size and histology are warranted. These studies will help establish multi-disciplinary treatment guidelines that improve local control while minimizing radiation necrosis during treatment of brain metastasis ≤3 cm.

Cesium-131 brachytherapy for the treatment of brain metastases: Current status and future perspectives

Adjuvant radiotherapy is often necessary following surgical resection of brain metastases to improve local tumor control and survival. Brachytherapy using cesium-131 offers a novel method for loco-regional radiotherapy. We reviewed the current literature reporting the use of cesium-131 brachytherapy for the treatment of brain metastases. Published studies and ongoing trials were reviewed to identify treatment protocols and clinical outcomes of cesium-131 brachytherapy for brain metastases. Cesium-131 brachytherapy was further compared to current outcomes for iodine-125 brachytherapy and stereotactic radiosurgery. Intraoperative brachytherapy allows patients to receive two treatment modalities in one setting while minimizing tumor cell repopulation. After initial interest, the use of iodine-125 brachytherapy has declined due to unfavorable rates of radiation necrosis without survival improvement. Recent data on intracavitary cesium-131 brachytherapy in brain metastases have demonstrated improved locoregional tumor control with low risks of radiation necrosis, with associated improvements in patients compliance and satisfaction. Cesium-131 isotope has a short half-life, delivers 90% of its dose within a month, shortens the time to initiation of systemic therapy compared to iodine-125 or external radiotherapy, and has an excellent radiation safety profile. Further analyses have demonstrated superior cost-effectiveness and quality-of-life improvement ratios of cesium-131 brachytherapy than adjuvant stereotactic radiosurgery. Cesium-131 brachytherapy is a safe and effective post-surgical treatment option for brain metastases with associated clinical and cost-effectiveness benefits in appropriately selected patients.

Dosimetric evaluation of iodine-125 brachytherapy for brain tumors using MR guidance combined with a three-dimensional non co-planar template

PURPOSE

To investigate the consistency between preoperative and postoperative dosimetry when ¹²⁵I brachytherapy for brain tumors is performed with magnetic resonance (MR) guidance and a three-dimensional non co-planar template (3DNPT).

METHODS AND MATERIALS

Thirty patients with brain tumors (metastatic or gliomas) underwent radioactive ¹²⁵I seed implantation. A preoperative treatment plan was determined with MR imaging, and the operation was done under 3DNPT assistance and MR guidance. The dosimetry was verified postoperatively based on postoperative CT-MR fusion images. Postoperative dosimetric parameters and implant quality indices were defined and compared with those in the preoperative treatment plan. Furthermore, a comparison of preoperative and postoperative doses to normal brain tissues and organs at risk was also performed.

RESULTS

All mean postoperative dosimetries were calculated. Target coverage parameters D90, D100, %CTV100, %CTV150, and %CTV200 were 143.6 cGy, 76.6 cGy, 88.2%, 63.1%, and 41.4%, respectively. The values of implant quality indices CI, EI, and HI were 0.75, 0.14, and 0.28, respectively. No significant differences between most preoperative and postoperative dosimetric parameters were found (p > 0.05). The differences were also insignificant for organs at risk. Postoperative %CTV150 and %CTV200 were higher than the preoperative, whereas postoperative HI was significantly lower than in the treatment plan.

CONCLUSIONS

Magnetic resonance guidance combined with 3DNPT allows accurate positioning and direction in ¹²⁵I brachytherapy for brain tumors. However, seed distribution and dose homogeneity require further improvement.

Feasibility of collagen matrix tiles with cesium-131 brachytherapy for use in the treatment of head and neck cancer

BACKGROUND

Locoregional failure is a unique and challenging problem in head and neck cancer with controversy surrounding the use of re-irradiation in the treatment. We aimed to evaluate the dosimetry and technical parameters in utilizing a collagen matrix with embedded Cesium-131 (Cs-131) radioactive isotope seeds as it relates to dose distribution and dose to carotid artery.

METHODS AND MATERIALS

Cadaveric feasibility study randomizing Cs-131 strands alone or Cs-131 with collagen matrix to be placed into neck dissection defects. For the dose computation, physicists employed the TG-43 dosimetry calculation algorithm with a point source assumption to compute the dose. Carotid arteries were contoured in MIM-Symphony software and the carotid artery maximum and mean doses were calculated in accordance with TG-43 specifications. Ease of use of collagen matrix tiles on a 7-point Likert scale and mean radiation dose to the carotid artery.

RESULTS

Ease of use score was higher in collagen matrix compared to stranded seeds with a mean score of 6.3 +/- 1.2 compared to 4.5 +/- 0.87. Time of implantation was statistically significantly, p = 0.031, lower in the collagen matrix group (M = 5.17 min, SD = 4.62) compared to stranded seeds (M = 15.83 min, SD = 3.24). Mean radiation dose to the carotid artery was 62.8 Gy +/- 9.46 in the collagen matrix group compared to 108.2 Gy +/- 55.6 in the traditional Cs-131 seeds group.

CONCLUSIONS

We present a feasibility and concept cadaveric study using a collagen matrix with Cesium-131 demonstrating preliminary evidence to support its ease of use, decreased time to implantation, and decreased dose delivered to the carotid artery.

Surgically targeted radiation therapy (STaRT) trials for brain neoplasms: A comprehensive review

The mainstays of radiation therapy include external beam radiation therapy (EBRT) and internally implanted radiation, or brachytherapy (BT), all with distinct benefits and risks in terms of local or distant tumor control and normal brain toxicities, respectively. GammaTile® Surgically Targeted Radiation Therapy (STaRT) attempts to limit the drawbacks of other BT paradigms via a permanently implanted, bioresorbable, conformable, collagen tile containing four uniform intensity radiation sources, thus preventing deleterious direct contact with the brain and optimizing interseed spacing to homogenous radiation exposure. The safety and feasibility of GammaTile® STaRT therapy was established by multiple clinical trials encompassing the spectrum of primary and secondary brain neoplasms, both recurrent and newly-diagnosed. Implantable GT tiles were FDA approved in 2018 for use in recurrent intracranial neoplasms, expanded to newly-diagnosed malignant intracranial neoplasms by 2020. The current spectrum of trials focuses on better defining the relative efficacy and safety of non-GT standard-of-care radiation strategies for intracranial brain neoplasm. We summarize the key design and eligibility criteria for open and future trials of GT therapy, including registries and randomized trials for newly-diagnosed and recurrent brain metastases as well as recurrent and newly-diagnosed glioblastoma in combination with approved therapies.

Medical Device Advances in the Treatment of Glioblastoma

Despite decades of research and the growing emergence of new treatment modalities, Glioblastoma (GBM) frustratingly remains an incurable brain cancer with largely stagnant 5-year survival outcomes of around 5%. Historically, a significant challenge has been the effective delivery of anti-cancer treatment. This review aims to summarize key innovations in the field of medical devices, developed either to improve the delivery of existing treatments, for example that of chemo-radiotherapy, or provide novel treatments using devices, such as sonodynamic therapy, thermotherapy and electric field therapy. It will highlight current as well as emerging device technologies, non-invasive versus invasive approaches, and by doing so provide a detailed summary of evidence from clinical studies and trials undertaken to date. Potential limitations and current challenges are discussed whilst also highlighting the exciting potential of this developing field. It is hoped that this review will serve as a useful primer for clinicians, scientists, and engineers in the field, united by a shared goal to translate medical device innovations to help improve treatment outcomes for patients with this devastating disease.

GammaTile: Comprehensive Review of a Novel Radioactive Intraoperative Seed-Loading Device for the Treatment of Brain Tumors

GammaTile is a Food and Drug Administration (FDA)-licensed device consisting of four cesium-131 (Cs-131) radiation-emitting seeds in the collagen tile about the postage stamp size. The tiles are utilized to line the brain cavity immediately after tumor resection. GammaTile therapy is a surgically targeted radiation therapy (STaRT) that helps provide instant, dose-intense treatment after the completion of resection. The objective of this study is to explore the safety and efficacy of GammaTile surgically targeted radiation therapy for brain tumors. This study also reviews the differences between GammaTile surgically targeted radiation therapy (STaRT) and other traditional treatment options for brain tumors. The electronic database searches utilized in this study include PubMed, Google Scholar, and ScienceDirect. A total of 4,150 articles were identified based on the search strategy. Out of these articles, 900 articles were retrieved. A total of 650 articles were excluded for various reasons, thus retrieving 250 citations. We applied the exclusion and inclusion criteria to these retrieved articles by screening their full text and excluding 180 articles. Therefore, 70 citations were retrieved and included in this comprehensive literature review, as outlined in the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) diagram. Based on the findings of this study, GammaTile surgically targeted radiation therapy (STaRT) is safe and effective for treating brain tumors. Similarly, the findings have also shown that the efficacy of GammaTile therapy can be enhanced by combining it with other standard-of-care treatment options/external beam radiation therapy (EBRT). Also, the results show that patients diagnosed with recurrent glioblastoma (GBM) exhibit poor median overall survival because of the possibility of the tumor returning. Therefore, combining STaRT with other standard-of-care treatment options/EBRT can improve the patient's overall survival (OS). GammaTile therapy enhances access to care, guarantees 100% compliance, and eliminates patients' need to travel regularly to hospitals for radiation treatments. Its implementation requires collaboration from various specialties, such as radiation oncology, medical physics, and neurosurgery.

Resection with intraoperative cesium-131 brachytherapy as salvage therapy for recurrent brain tumors

OBJECTIVE

The authors' objective was to examine the safety and efficacy of salvage intracranial cesium-131 brachytherapy in combination with resection of recurrent brain tumors.

METHODS

The authors conducted a retrospective chart review of consecutive patients treated with intraoperative intracranial cesium-131 brachytherapy at a single institution. Permanent suture-stranded cesium-131 seeds were implanted in the resection cavity after maximal safe tumor resection. The primary outcomes of interest were local, locoregional (within 1 cm), and intracranial control, as well as rates of overall survival (OS), neurological death, symptomatic adverse radiation effects (AREs), and surgical complication rate graded according to Common Terminology Criteria for Adverse Events version 5.0.

RESULTS

Between 2016 and 2020, 36 patients received 40 consecutive cesium-131 implants for 42 recurrent brain tumors and received imaging follow-up for a median (interquartile range [IQR]) of 17.0 (12.7-25.9) months. Twenty patients (55.6%) with 22 implants were treated for recurrent brain metastasis, 12 patients (33.3%) with 16 implants were treated for recurrent atypical (n = 7) or anaplastic (n = 5) meningioma, and 4 patients (11.1%) were treated for other recurrent primary brain neoplasms. All except 1 tumor (97.6%) had received prior radiotherapy, including 20 (47.6%) that underwent 2 or more prior radiotherapy treatments and 23 (54.8%) that underwent prior resection. The median (IQR) tumor size was 3.0 (2.3-3.7) cm, and 17 lesions (40.5%) had radiographic evidence of ARE prior to salvage therapy. Actuarial 1-year local/locoregional/intracranial control rates for the whole cohort and patients with metastases and meningiomas were 91.6%/83.4%/47.9%, 88.8%/84.4%/45.4%, and 100%/83.9%/46.4%, respectively. No cases of local recurrence of any histology (0 of 27) occurred after gross-total resection (p = 0.012, log-rank test). The 1-year OS rates for the whole cohort and patients with metastases and meningiomas were 82.7%, 79.1%, and 91.7%, respectively, and the median (IQR) survival of all patients was 26.7 (15.6-36.4) months. Seven patients (19.4%) experienced neurological death from progressive intracranial disease (7 of 14 total deaths [50%]), 5 (13.9%) of whom died of leptomeningeal disease. Symptomatic AREs were observed in 9.5% of resection cavities (n = 4), of which 1 (2.4%) was grade 3 in severity. The surgical complication rate was 16.7% (n = 7); 4 (9.5%) of these patients had grade 3 or higher complications, including 1 patient (2.4%) who died perioperatively.

CONCLUSIONS

Cesium-131 brachytherapy resulted in good local control and acceptable rates of symptomatic AREs and surgical complications in this heavily pretreated cohort, and it may be a reasonable salvage adjuvant treatment for this patient population.

Neoadjuvant Stereotactic Radiotherapy for Brain Metastases: Systematic Review and Meta-Analysis of the Literature and Ongoing Clinical Trials

Simple Summary

The available treatment strategies for patients with brain metastases remain suboptimal, with current research focused on identifying therapies intended to improve patient outcomes while reducing the risk of treatment-related complications. Several studies have investigated the role of pre-operative neoadjuvant stereotactic radiotherapy, and have proposed it as a valid alternative to post-operative adjuvant stereotactic radiotherapy. The aim of our systematic review was to comprehensively analyze the current literature and ongoing clinical trials evaluating neoadjuvant stereotactic radiotherapy in patients with brain metastases, describing treatment protocols and related outcomes. Early evidence suggests that neoadjuvant stereotactic radiotherapy may offer rates of local control and overall survival comparable to those obtained with adjuvant postoperative SRS, but comparative studies are currently lacking. In addition, neoadjuvant stereotactic radiotherapy shows low rates of post-treatment radiation necrosis and leptomeningeal metastases. Ongoing clinical trials aim to evaluate long-term outcomes in large patient cohorts, with some focused on comparing neoadjuvant stereotactic radiotherapy to adjuvant stereotactic radiosurgery.

Abstract

Background: Brain metastases (BMs) carry a high morbidity and mortality burden. Neoadjuvant stereotactic radiotherapy (NaSRT) has shown promising results. We systematically reviewed the literature on NaSRT for BMs. Methods: PubMed, EMBASE, Scopus, Web-of-Science, Cochrane, and ClinicalTrial.gov were searched following the PRISMA guidelines to include studies and ongoing trials reporting NaSRT for BMs. Indications, protocols, and outcomes were analyzed using indirect random-effect meta-analyses. Results: We included 7 studies comprising 460 patients with 483 BMs, and 13 ongoing trials. Most BMs originated from non-small lung cell carcinoma (41.4%), breast cancer (18.7%) and melanoma (43.6%). Most patients had single-BM (69.8%) located supratentorial (77.8%). Patients were eligible if they had histologically-proven primary tumors and ≤4 synchronous BMs candidate for non-urgent surgery and radiation. Patients with primary tumors clinically responsive to radiotherapy, prior brain radiation, and leptomeningeal metastases were deemed non-eligible. Median planning target volume was 9.9 cm³ (range, 2.9–57.1), and NaSRT was delivered in 1-fraction (90.9%), 5-fraction (4.8%), or 3-fraction (4.3%), with a median biological effective dose of 39.6 Gy10 (range, 35.7–60). Most patients received piecemeal (76.3%) and gross-total (94%) resection after a median of 1-day (range, 1–10) post-NaSRT. Median follow-up was 19.2-months (range, 1–41.3). Actuarial post-treatment rates were 4% (95%CI: 2–6%) for symptomatic radiation necrosis, 15% (95%CI: 12–18%) and 47% (95%CI: 42–52%) for local and distant recurrences, 6% (95%CI: 3–8%) for leptomeningeal metastases, 81% (95%CI: 75–87%) and 59% (95%CI: 54–63%) for 1-year local tumor control and overall survival. Conclusion: NaSRT is effective and safe for BMs. Ongoing trials will provide high-level evidence on long-term post-treatment outcomes, further compared to adjuvant stereotactic radiotherapy.

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.

Review of Current Principles of the Diagnosis and Management of Brain Metastases

Brain metastases are the most common intracranial tumors and are increasing in incidence as overall cancer survival improves. Diagnosis of brain metastases involves both clinical examination and magnetic resonance imaging. Treatment may involve a combination of surgery, radiotherapy, and systemic medical therapy depending on the patient's neurologic status, performance status, and overall oncologic burden. Advances in these domains have substantially impacted the management of brain metastases and improved performance status and survival for some patients. Indications for surgery have expanded with improved patient selection, imaging, and intraoperative monitoring. Robust evidence supports the use of whole brain radiotherapy and stereotactic radiosurgery, for both standalone and adjuvant indications, in almost all patients. Lastly, while systemic medical therapy has historically provided little benefit, modern immunotherapeutic agents have demonstrated promise. Current investigation seeks to determine the utility of neoadjuvant radiotherapy and laser interstitial thermal therapy, which have shown benefit in limited studies to date. This article provides a review of the epidemiology, pathology, diagnosis, and treatment of brain metastases and the corresponding supporting evidence.

Brachytherapy for central nervous system tumors

Radiation is a mainstay of treatment for central nervous system (CNS) tumors. Brachytherapy involves the placement of a localized/interstitial radiation source into a tumor or resection bed and has distinct advantages that can make it an attractive form of radiation when used in the appropriate setting. However, the data supporting use of brachytherapy is clouded by variability in radiation sources, techniques, delivered doses, and trial designs. The goal of this manuscript is to identify consistent themes, review the highest-level evidence and potential indications for brachytherapy in CNS tumors, as well as highlight avenues for future work. Improved understanding of the underlying biology, indications, complications, and evolving industry-academic collaborations, place brachytherapy on the brink of a resurgence.

Radiofrequency Ablation Combined with Radioactive Seed Implantation for Nonsmall Cell Lung Cancer

The aim of this study is to investigate the value of radiofrequency ablation combined with radioactive seed implantation in nonsmall cell lung cancer treatment. 30 patients with primary nonsmall cell lung cancer were randomly divided into two groups. Group A was treated with radiofrequency ablation combined with radiation seed implantation, and group B was treated with radiofrequency ablation only. We compared the incidence of complications in the two groups and reviewed the effective percentage every 3 months. All patients were treated successfully, and there were no deaths during treatment. There were no deaths and no cases of distant organ metastasis in nine months of follow-up. There were no significant differences in treatment-related complications between the two groups. The early postoperative (three and six months) effective percentage was not significantly different (P > 0.05). After 9 months, the postoperative effective rate for group A (9/15) was significantly different from that for group B (radiofrequency ablation) (6/15) (P < 0.05). Radiofrequency ablation combined with radiation 125I seed implantation can complement each other in the treatment of nonsmall cell lung cancer.

Early Therapeutic Interventions for Newly Diagnosed Glioblastoma: Rationale and Review of the Literature

PURPOSE OF REVIEW

Glioblastoma is the commonest primary brain cancer in adults whose outcomes are amongst the worst of any cancer. The current treatment pathway comprises surgery and postoperative chemoradiotherapy though unresectable diffusely infiltrative tumour cells remain untreated for several weeks post-diagnosis. Intratumoural heterogeneity combined with increased hypoxia in the postoperative tumour microenvironment potentially decreases the efficacy of adjuvant interventions and fails to prevent early postoperative regrowth, called rapid early progression (REP). In this review, we discuss the clinical implications and biological foundations of post-surgery REP. Subsequently, clinical interventions potentially targeting this phenomenon are reviewed systematically.

RECENT FINDINGS

Early interventions include early systemic chemotherapy, neoadjuvant immunotherapy, local therapies delivered during surgery (including Gliadel wafers, nanoparticles and stem cell therapy) and several radiotherapy techniques. We critically appraise and compare these strategies in terms of their efficacy, toxicity, challenges and potential to prolong survival. Finally, we discuss the most promising strategies that could benefit future glioblastoma patients. There is biological rationale to suggest that early interventions could improve the outcome of glioblastoma patients and they should be investigated in future trials.

A multidisciplinary management algorithm for brain metastases

The incidence of brain metastases continues to present a management issue despite the advent of improved systemic control and overall survival. While the management of oligometastatic disease (ie, 1-4 brain metastases) with surgery and radiation has become fairly straightforward in the era of radiosurgery, the management of patients with multiple metastatic brain lesions can be challenging. Here we review the available evidence and provide a multidisciplinary management algorithm for brain metastases that incorporates the latest advances in surgery, radiation therapy, and systemic therapy while taking into account the latest in precision medicine-guided therapies. In particular, we argue that whole-brain radiation therapy can likely be omitted in most patients as up-front therapy.

Dosimetric Impacts of Source Migration, Radioisotope Type, and Decay with Permanent Implantable Collagen Tile Brachytherapy for Brain Tumors

Introduction: Brachytherapy using permanently implantable collagen tiles containing cesium-131 (Cs-131) is indicated for treatment of malignant intracranial neoplasms. We quantified Cs-131 source migration and modeled the resulting dosimetric impact for Cs-131, iodine-125 (I-125), and palladium-103 (Pd-103). Methods and Materials: This was a retrospective analysis of a subgroup of patients enrolled in a prospective, single-center, nonrandomized, clinical trial (NCT03088579) of Cs-131 collagen tile brachytherapy. Postimplant Cs-131 plans and hypothetical I-125 and Pd-103 calculations were compared for 20 glioblastoma patients for a set seed geometry. Dosimetric impact of decay and seed migration was calculated for 2 hypothetical scenarios: Scenario 1, assuming seed positions on a given image set were unchanged until acquisition of the subsequent set; Scenario 2, assuming any change in seed positions occurred the day following acquisition of the prior images. Seed migration over time was quantified for a subset of 7 patients who underwent subsequent image-guided radiotherapy. Results: Mean seed migration was 1.7 mm (range: 0.7-3.1); maximum seed migration was 4.3 mm. Mean dose to the 60 Gy volume differed by 0.4 Gy (0.6%, range 0.1-1.0) and 0.9 Gy (1.5%, range 0.2-1.7) for Cs-131, 1.2 Gy (2.0%, range 0.1-2.1) and 1.6 Gy (2.6%, range 1.2-2.6) for I-125, and 0.8 Gy (1.3%, range 0.2-1.5) and 1.4 Gy (2.3%, range 0.3-1.9) for Pd-103, for Scenarios 1 and 2, respectively, compared with the postimplant plan. For a set seed geometry mean implant dose was higher for Pd-103 (1.3 times) and I-125 (1.1 times) versus Cs-131. Dose fall-off was steepest for Pd-103: gradient index 1.88 versus 2.23 (I-125) and 2.40 (Cs-131). Conclusions: Dose differences due to source migration were relatively small, suggesting robust prevention of seed migration from Cs-131-containing collagen tiles. Intratarget heterogeneity was greater with Pd-103 and I-125 than Cs-131. Dose fall-off was fastest with Pd-103 followed by I-125 and then Cs-131.

Surgical Outcomes of Novel Collagen Tile Cesium Brachytherapy for Recurrent Intracranial Tumors at a Tertiary Referral Center

Treatment for recurrent intracranial neoplasms is often difficult and less standardized. Since its approval by the Food & Drug Administration (FDA), GammaTile^TM (GT, GT Medical Technologies, Tempe, AZ), a novel collagen tile cesium brachytherapy, has been investigated for use in this population. This study presents the initial experience with the use of GT for patients with recurrent intracranial neoplasms at a tertiary referral center. A retrospective analysis of all patients with GT implantation from November 2019 to July 2021 was performed. Information regarding demographics, clinical history, imaging data, prior tumor treatment, dosing, surgical complications, and outcomes was collected. Twelve patients were included in this study. Pathologies included gliomas (five patients), meningiomas (five patients), and metastatic tumors (two patients). The median tumor volume treated was 24 cc (IQR: 21.2 - 31.3 cc), and patients had a median of 7.5 tiles implanted (IQR: 5.4 - 10.3). One patient had a delayed epidural hematoma requiring reoperation, which was unrelated to GT implantation. Median follow-up was seven months (IQR: 3 -10), with the longest follow-up time of 20 months. Two patients have had local disease recurrence and three patients have had systemic progression of their disease. Three patients are deceased with survivals of 2.9, 4.8, and 5.8 months. Collagen tile brachytherapy is a safe and viable option for patients with recurrent intracranial tumors. Our data are consistent with early results seen at other institutions. Long-term data with larger patient populations are required to assess efficacy, safety, and indications for the use of this novel technology.

Multimodality durable salvage of recurrent brain metastases refractory to LITT, SRS and immunotherapy with resection and cesium-131 brachytherapy: case report and literature review

Brain metastases (BrM) are treated with multimodality therapy, however the optimal combination and timing of modalities in the setting of recurrent tumours that have failed prior treatments remain poorly defined. We present a case of a patient with biopsy-confirmed renal cell carcinoma BrM with good performance status initially treated with laser interstitial thermal ablation therapy (LITT) followed by stereotactic radiosurgery and dual checkpoint inhibitor immunotherapy. He subsequently developed rapid in-field recurrence which was treated with salvage surgical resection and implantation of intracavitary cesium-131 brachytherapy. The patient's disease remained stable through 18 months postoperatively. This case illustrates the range of options available and provides a combination salvage therapy strategy in a select group of locally recurrent patients who have exhausted conventional treatment options.

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

OBJECTIVE

Publications on adjuvant stereotactic radiosurgery (SRS) are largely limited to patients completing SRS within a specified time frame. The authors assessed real-world local recurrence (LR) for all brain metastasis (BM) patients referred for SRS and identified predictors of SRS timing.

METHODS

The authors retrospectively identified BM patients undergoing resection and referred for SRS between 2012 and 2018. Patients were categorized by time to SRS, as follows: 1) ≤ 4 weeks, 2) > 4-8 weeks, 3) > 8 weeks, and 4) never completed. The relationships between timing of SRS and LR, LR-free survival (LRFS), and survival were investigated, as well as predictors of and reasons for specific SRS timing.

RESULTS

In a cohort of 159 patients, the median age at resection was 64.0 years, 56.5% of patients were female, and 57.2% were in recursive partitioning analysis (RPA) class II. The median preoperative tumor diameter was 2.9 cm, and gross-total resection was achieved in 83.0% of patients. All patients were referred for SRS, but 20 (12.6%) did not receive it. The LR rate was 22.6%, and the time to SRS was correlated with the LR rate: 2.3% for patients receiving SRS at ≤ 4 weeks postoperatively, 14.5% for SRS at > 4-8 weeks (p = 0.03), and 48.5% for SRS at > 8 weeks (p < 0.001). No LR difference was seen between patients whose SRS was delayed by > 8 weeks and those who never completed SRS (48.5% vs 50.0%; p = 0.91). A similar relationship emerged between time to SRS and LRFS (p < 0.01). Non-small cell lung cancer pathology (p = 0.04), earlier year of treatment (p < 0.01), and interval from brain MRI to SRS (p < 0.01) were associated with longer intervals to SRS. The rates of receipt of systemic therapy also differed significantly between patients by category of time to SRS (p = 0.02). The most common reasons for intervals of > 4-8 weeks were logistic, whereas longer delays or no SRS were caused by management of systemic disease or comorbidities.

CONCLUSIONS

Available data on LR rates after adjuvant SRS are often obtained from carefully preselected patients receiving timely treatment, whereas significantly less information is available on the efficacy of adjuvant SRS in patients treated under "real-world" conditions. Management of these patients may merit reconsideration, particularly when SRS is not delivered within ≤ 4 weeks of resection. The results of this study indicate that a substantial number of patients referred for SRS either never receive it or are treated > 8 weeks postoperatively, at which time the SRS-treated patients have an LR risk equivalent to that of patients who never received SRS. Increased attention to the reasons for prolonged intervals from surgery to SRS and strategies for reducing them is needed to optimize treatment. For patients likely to experience delays, other radiotherapy techniques may be considered.

Salvage resection of recurrent previously irradiated brain metastases: tumor control and radiation necrosis dependency on adjuvant re-irradiation

PURPOSE

The efficacy of salvage resection (SR) of recurrent brain metastases (rBrM) following stereotactic radiosurgery (SRS) is undefined. We sought to describe local recurrence (LR) and radiation necrosis (RN) rates in patients undergoing SR, with or without adjuvant post-salvage radiation therapy (PSRT).

METHODS

A retrospective cohort study evaluated patients undergoing SR of post-SRS rBrM between 3/2003-2/2020 at an NCI-designated cancer center. Cases with histologically-viable malignancy were stratified by receipt of adjuvant PSRT within 60 days of SR. Clinical outcomes were described using cumulative incidences in the clustered competing-risks setting, competing risks regression, and Kaplan-Meier methodology.

RESULTS

One-hundred fifty-five rBrM in 135 patients were evaluated. The overall rate of LR was 40.2% (95% CI 34.3-47.2%) at 12 months. Thirty-nine (25.2%) rBrM treated with SR + PSRT trended towards lower 12-month LR versus SR alone [28.8% (95% CI 17.0-48.8%) versus 43.9% (95% CI 36.2-53.4%), p = .07 by multivariate analysis]. SR as re-operation (p = .03) and subtotal resection (p = .01) were independently associated with higher rates of LR. On univariate analysis, tumor size (p = .48), primary malignancy (p = .35), and PSRT technique (p = .43) bore no influence on LR. SR + PSRT was associated with an increased risk of radiographic RN at 12 months versus SR alone [13.4% (95% CI 5.5-32.7%) versus 3.5% (95% CI 1.5-8.0%), p = .02], though the percentage with symptomatic RN remained low (5.1% versus 0.9%, respectively). Median overall survival from SR was 13.4 months (95% CI 10.5-17.7).

CONCLUSION

In this largest-known series evaluating SR outcomes in histopathologically-confirmed rBrM, we identify a significant LR risk that may be reduced with adjuvant PSRT and with minimal symptomatic RN. Prospective analysis is warranted.

Surgical advances in the management of brain metastases

As the epidemiological and clinical burden of brain metastases continues to grow, advances in neurosurgical care are imperative. From standard magnetic resonance imaging (MRI) sequences to functional neuroimaging, preoperative workups for metastatic disease allow high-resolution detection of lesions and at-risk structures, facilitating safe and effective surgical planning. Minimally invasive neurosurgical approaches, including keyhole craniotomies and tubular retractors, optimize the preservation of normal parenchyma without compromising extent of resection. Supramarginal surgery has pushed the boundaries of achieving complete removal of metastases without recurrence, especially in eloquent regions when paired with intraoperative neuromonitoring. Brachytherapy has highlighted the potential of locally delivering therapeutic agents to the resection cavity with high rates of local control. Neuronavigation has become a cornerstone of operative workflow, while intraoperative ultrasound (iUS) and intraoperative brain mapping generate real-time renderings of the brain unaffected by brain shift. Endoscopes, exoscopes, and fluorescent-guided surgery enable increasingly high-definition visualizations of metastatic lesions that were previously difficult to achieve. Pushed forward by these multidisciplinary innovations, neurosurgery has never been a safer, more effective treatment for patients with brain metastases.

Recommendations for intraoperative mesh brachytherapy: Report of AAPM Task Group No. 222

Mesh brachytherapy is a special type of a permanent brachytherapy implant: it uses low-energy radioactive seeds in an absorbable mesh that is sutured onto the tumor bed immediately after a surgical resection. This treatment offers low additional risk to the patient as the implant procedure is carried out as part of the tumor resection surgery. Mesh brachytherapy utilizes identification of the tumor bed through direct visual evaluation during surgery or medical imaging following surgery through radiographic imaging of radio-opaque markers within the sources located on the tumor bed. Thus, mesh brachytherapy is customizable for individual patients. Mesh brachytherapy is an intraoperative procedure involving mesh implantation and potentially real-time treatment planning while the patient is under general anesthesia. The procedure is multidisciplinary and requires the complex coordination of multiple medical specialties. The preimplant dosimetry calculation can be performed days beforehand or expediently in the operating room with the use of lookup tables. In this report, the guidelines of American Association of Physicists in Medicine (AAPM) are presented on the physics aspects of mesh brachytherapy. It describes the selection of radioactive sources, design and preparation of the mesh, preimplant treatment planning using a Task Group (TG) 43-based lookup table, and postimplant dosimetric evaluation using the TG-43 formalism or advanced algorithms. It introduces quality metrics for the mesh implant and presents an example of a risk analysis based on the AAPM TG-100 report. Recommendations include that the preimplant treatment plan be based upon the TG-43 dose calculation formalism with the point source approximation, and the postimplant dosimetric evaluation be performed by using either the TG-43 approach, or preferably the newer model-based algorithms (viz., TG-186 report) if available to account for effects of material heterogeneities. To comply with the written directive and regulations governing the medical use of radionuclides, this report recommends that the prescription and written directive be based upon the implanted source strength, not target-volume dose coverage. The dose delivered by mesh implants can vary and depends upon multiple factors, such as postsurgery recovery and distortions in the implant shape over time. For the sake of consistency necessary for outcome analysis, prescriptions based on the lookup table (with selection of the intended dose, depth, and treatment area) are recommended, but the use of more advanced techniques that can account for real situations, such as material heterogeneities, implant geometric perturbations, and changes in source orientations, is encouraged in the dosimetric evaluation. The clinical workflow, logistics, and precautions are also presented.

Surgical resection versus stereotactic radiosurgery on local recurrence and survival for patients with a single brain metastasis: a systematic review and meta-analysis

BACKGROUND

Brain metastases (BM) are the most frequent intracranial tumours in adults. In patients with solitary BM, surgical resection (SR) or stereotactic radiosurgery (SRS) is performed. There is limited evidence comparing one treatment over the other.

OBJECTIVE

To compare SR versus SRS on patients with solitary BMs, regarding local recurrence (LR) and overall survival (OS) conducting a systematic review and meta-analysis.

METHODS

Systematic review of literature following PRISMA guidelines, using the databases of Medline, Clinicaltrials.gov, Embase, Web of Science, Sciencedirect, CINAHL, Wiley Online Library, Springerlink and LILACS. Following study selection based on inclusion and exclusion criteria, data extraction and a critical analysis of the literature was performed according to the GRADE scale. For quantitative analysis, a random effects model was used. Data were synthetized and evaluated on a forest plot and funnel plot.

RESULTS

Two randomized clinical trials, four cohort studies and one case-control studies met our inclusion criteria for the qualitative analysis. None was excluded subsequently. Overall, 614 patients with single metastasis were included. Studies had high heterogeneity. Multiple significant variables affecting the outcome were signalized. Meta-analysis showed no significant differences for survival (HR, 1.10; 95% CI, 0.75-1.45) or LR (HR, 0.81; 95% CI, 0.42-1.20).

CONCLUSIONS

According to current evidence, in patients with a single small metastasis there is no statistically significant difference in OS or LR among the chosen techniques (SR or SRS). Multiple significant co-variables may affect both outcomes. Different outcomes better than OS should be evaluated in further randomized studies.

Cs-131 brachytherapy for patients with recurrent glioblastoma combined with bevacizumab avoids radiation necrosis while maintaining local control

PURPOSE

Re-irradiation of recurrent glioblastoma (GBM) may delay further recurrence but re-irradiation increases the risk of radionecrosis (RN). Salvage therapy should focus on balancing local control (LC) and toxicity. We report the results of using intraoperative Cesium-131 (Cs-131) brachytherapy for recurrent GBM in a population of patients who also received bevacizumab.

METHODS AND MATERIALS

Twenty patients with recurrent GBM underwent maximally safe neurosurgical resection with Cs-131 brachytherapy between 2010 and 2015. Eighty Gy was prescribed to 0.5 cm from the surface of the resection cavity. All patients previously received adjuvant radiotherapy and temozolomide, and received bevacizumab before or after salvage brachytherapy. Seven of 20 (35%) tumors were multiply recurrent and had been previously salvaged with external beam radiotherapy. Patients received MRI scans every 2 months monitored for recurrence, progression, and RN.

RESULTS

Median tumor diameter was 4.65 cm (range, 1.2-6.3 cm). Median number of seeds pace was 41 (range, 20-74) with total seed activity 96.8U (range, 41.08-201.3U). At a median followup of 19 months, crude LC was 85% and median overall survival was 9 months (range, 5-26 months). There were two postoperative wound infections (10%), three seizures (15%), and 0% incidence of RN.

CONCLUSIONS

Our study demonstrates that while LC and survival are similar to other studies of postoperative external beam radiotherapy, no RN occurred in any of these patients, including 7 multiply re-irradiated patients. Of interest, there were patients with multiple recurrences whose survival extended beyond 20 months. These findings suggest that the use of highly conformal Cs-131 brachytherapy is a promising treatment for patients with recurrent GBM with minimal risk of development of RN.

A matched-pair analysis of clinical outcomes after intracavitary cesium-131 brachytherapy versus stereotactic radiosurgery for resected brain metastases

OBJECTIVE

Adjuvant radiation therapy (RT), such as cesium-131 (Cs-131) brachytherapy or stereotactic radiosurgery (SRS), reduces local recurrence (LR) of brain metastases (BM). However, SRS is less efficacious for large cavities, and the delay between surgery and SRS may permit tumor repopulation. Cs-131 has demonstrated improved local control, with reduced radiation necrosis (RN) compared to SRS. This study represents the first comparison of outcomes between Cs-131 brachytherapy and SRS for resected BM.

METHODS

Patients with BM treated with Cs-131 and SRS following gross-total resection were retrospectively identified. Thirty patients who underwent Cs-131 brachytherapy were compared to 60 controls who received SRS. Controls were selected from a larger cohort to match the patients treated with Cs-131 in a 2:1 ratio according to tumor size, histology, performance status, and recursive partitioning analysis class. Overall survival (OS), LR, regional recurrence, distant recurrence (DR), and RN were compared.

RESULTS

With a median follow-up of 17.5 months for Cs-131-treated and 13.0 months for SRS-treated patients, the LR rate was significantly lower with brachytherapy; 10% for the Cs-131 cohort compared to 28.3% for SRS patients (OR 0.281, 95% CI 0.082-0.949; p = 0.049). Rates of regional recurrence, DR, and OS did not differ significantly between the two cohorts. Kaplan-Meier analysis with log-rank testing showed a significantly higher likelihood of freedom from LR (p = 0.027) as well as DR (p = 0.018) after Cs-131 compared to SRS treatment (p = 0.027), but no difference in likelihood of OS (p = 0.093). Six (10.0%) patients who underwent SRS experienced RN compared to 1 (3.3%) patient who received Cs-131 (p = 0.417).

CONCLUSIONS

Postresection patients with BM treated with Cs-131 brachytherapy were more likely to achieve local control compared to SRS-treated patients. This study provides preliminary evidence of the potential of Cs-131 to reduce LR following gross-total resection of single BM, with minimal toxicity, and suggests the need for a prospective study to address this question.

Heterogeneity of radiation response in mesenchymal subtype glioblastoma: molecular profiling and reactive oxygen species generation

BACKGROUND

Radiotherapy-induced tumor death remains critical in the successful first-line management of glioblastoma, whereas resistance to radiation serves as a major factor in disease progression. Mesenchymal shift has been identified as a driver in GBM recurrence, with gene expression associated with enhanced repair of macromolecular damage caused by radiation.

METHODS

Using distinct mesenchymal subtype GBM cells lines, radiation response was assessed by clonogenic assay and orthotopic mouse tumor model. RNA-sequencing was performed in the setting of increasing radiation dosing while real-time assessment of ROS generation was achieved by the measurement of hydroxyl spin trap adducts via electron paramagnetic resonance.

RESULTS

Radiation-induced cell death determined by clonogenic assay was significantly different at low dose (4-8 Gy) between the resistant U3035 cells and the sensitive U3020 cells. Similar trends were present in the in vivo NSG mouse model following radiation dosing on post-implantation day 7-10, with the rate of reduction in tumor bioluminescence reversing between the U3020 and U3035 cells after the third dose of radiation. Changes in gene expression following radiation determined by RNA-sequencing indicate both U3035 and U3020 cells demonstrate a shift toward more mesenchymal profiles, with concurrent shift away from pro-neural subtype gene expression in the U3020 cells that appeared to develop resistance to radiation in vivo. Persistence of ROS generated following radiation was greater in U3020 cells shown to be more sensitive to radiation.

CONCLUSIONS

Despite the same molecular classification, distinct GBM cell lines can demonstrate differential response to radiation and potential for mesenchymal shift associated with radiation resistance.

First clinical implementation of GammaTile permanent brain implants after FDA clearance

PURPOSE

GammaTile cesium-131 (¹³¹Cs) permanent brain implant has received Food and Drug Administration (FDA) clearance as a promising treatment for certain brain tumors. Our center was the first institution in the United States after FDA clearance to offer the clinical use of GammaTile brachytherapy outside of a clinical trial. The purpose of this work is to aid the medical physicist and radiation oncologist in implementing this collagen carrier tile brachytherapy (CTBT) program in their practice.

METHODS

A total of 23 patients have been treated with GammaTile to date at our center. Treatment planning system (TPS) commissioning was performed by configuring the parameters for the ¹³¹Cs (IsoRay Model CS-1, Rev2) source, and doses were validated with the consensus data from the American Association of Physicists in Medicine TG-43U1S2. Implant procedures, dosimetry, postimplant planning, and target delineations were established based on our clinical experience. Radiation safety aspects were evaluated based on exposure rate measurements of implanted patients, as well as body and ring badge measurements.

RESULTS

An estimated timeframe of the GammaTile clinical responsibilities for the medical physicist, radiation oncologist, and neurosurgeon is presented. TPS doses were validated with published dose to water for ¹³¹Cs. Clinical aspects, including estimation of the number of tiles, treatment planning, dosimetry, and radiation safety considerations, are presented.

CONCLUSION

The implementation of the GammaTile program requires collaboration from multiple specialties, including medical physics, radiation oncology, and neurosurgery. This manuscript provides a roadmap for the implementation of this therapy.

Durable 5-year local control for resected brain metastases with early adjuvant SRS: the effect of timing on intended-field control

Background

Adjuvant stereotactic radiosurgery (SRS) improves the local control of resected brain metastases (BrM). However, the dependency of long-term outcomes on SRS timing relative to surgery remains unclear.

Methods

Retrospective analysis of patients treated with metastasectomy-plus-adjuvant SRS at Memorial Sloan Kettering Cancer Center (MSK) between 2013 and 2016 was conducted. Kaplan-Meier methodology was used to describe overall survival (OS) and cumulative incidence rates were estimated by type of recurrence, accounting for death as a competing event. Recursive partitioning analysis (RPA) and competing risks regression modeling assessed prognostic variables and associated events of interest.

Results

Two hundred and eighty-two patients with BrM had a median OS of 1.5 years (95% CI: 1.2-2.1) from adjuvant SRS with median follow-up of 49.8 months for survivors. Local surgical recurrence, other simultaneously SRS-irradiated site recurrence, and distant central nervous system (CNS) progression rates were 14.3% (95% CI: 10.1-18.5), 4.9% (95% CI: 2.3-7.5), and 47.5% (95% CI: 41.4-53.6) at 5 years, respectively. Median time-to-adjuvant SRS (TT-SRS) was 34 days (IQR: 27-39). TT-SRS was significantly associated with surgical site recurrence rate (P = 0.0008). SRS delivered within 1 month resulted in surgical site recurrence rate of 6.1% (95% CI: 1.3-10.9) at 1-year, compared to 9.2% (95% CI: 4.9-13.6) if delivered between 1 and 2 months, or 27.3% (95% CI: 0.0-55.5) if delivered >2 months after surgery. OS was significantly lower for patients with TT-SRS >~2 months. Postoperative length of stay, discharge to a rehabilitation facility, urgent care visits, and/or disease recurrence between surgery and adjuvant SRS associated with increased TT-SRS.

Conclusions

Adjuvant SRS provides durable local control. However, delays in initiation of postoperative SRS can decrease its efficacy.

Dosimetric differences between cesium-131 and iodine-125 brachytherapy for the treatment of resected brain metastases

Purpose

To compare treatment plans and evaluate dosimetric characteristics of permanent cesium-131 (¹³¹Cs) vs. iodine-125 (¹²⁵I) implants used in brain brachytherapy.

Material and methods

Twenty-four patients with ¹³¹Cs implants from a prospective phase I/II trial were re-planned with ¹²⁵I implants. In order to evaluate the volume of brain tissue exposed to radiation therapy (RT), the dose volume histogram was generated for both radioisotopes. To evaluate the dosimetric differences of the two radioisotopes we compared homogeneity (HI) and conformity indices (CI), and dose covering 100% (D₁₀₀), 90% (D₉₀), 80% (D₈₀), and 50% (D₅₀) of the clinical target volume (CTV).

Results

At the 100%, 90%, 80%, and 50% isodose lines, the ¹³¹Cs plans exposed less mean volume of brain tissue than the ¹²⁵I plans (p < 0.001). The D₁₀₀, D₉₀, D₈₀, and D₅₀ were smaller for ¹³¹Cs (p < 0.001). The HI and CI for ¹³¹Cs vs. ¹²⁵I were 19.71 vs. 29.04 and 1.31 vs. 1.92, respectively (p < 0.001).

Conclusions

Compared to ¹²⁵I, ¹³¹Cs exposed smaller volumes of brain tissue to equivalent doses of radiation and delivered lower radiation doses to equivalent volumes of the CTV. ¹³¹Cs exhibited a higher HI, indicating increased uniformity of doses within the CTV. Lastly, ¹³¹Cs presented a CI closer to 1, indicating that the total volume receiving the prescription dose was closer to the desired CTV volume. These results suggest that ¹³¹Cs is dosimetrically superior to ¹²⁵I and may explain the reason for the 0% incidence of radiation necrosis (RN) in our previously published prospective study using ¹³¹Cs.

GammaTile®: Surgically targeted radiation therapy for glioblastomas

Glioblastoma is the most common primary malignant neoplasm of the central nervous system in adults. Standard of care is resection followed by chemo-radiation therapy. Despite this aggressive approach, >80% of glioblastomas recur in proximity to the resection cavity. Brachytherapy is an attractive strategy for improving local control. GammaTile^® is a newly US FDA-cleared device which incorporates ¹³¹Cs radiation emitting seeds in a resorbable collagen-based carrier tile for surgically targeted radiation therapy to achieve highly conformal radiation at the time of surgery. Embedding encapsulated ¹³¹Cs radiation emitter seeds in collagen-based tiles significantly lowers the technical barriers associated with traditional brachytherapy. In this review, we highlight the potential of surgically targeted radiation therapy and the currently available data for this novel approach.

Evolving Strategies to Potentially Further Optimize Surgical Interventions in Brain Cancer

PURPOSE OF REVIEW

Provide an overview, the indications for use, and a synopsis of current literature regarding two evolving neurosurgical interventions-GammaTile therapy (GTT) and laser interstitial thermal therapy (LITT).

RECENT FINDINGS

GTT delivers immediate, uniform, high-dose radiation with avoidance of direct brain-to-seed contact. Innate properties of the novel carrier system and cesium-131 source may explain lower observed rate of radiation-induced necrosis (RIN) and support use in larger and previously irradiated lesions. LITT delivers focal laser energy to cause heat-generated necrosis. Case series suggest use in difficult-to-access lesions and treatment of RIN. Collaboration among subspecialties and remaining up-to-date on evolving technology is critical in developing individualized treatment plans for patients with brain cancer. While patients should be thoroughly counseled that these interventions are not standard of care, in optimal clinical scenarios, GTT and LITT could extend quantity and quality of life for patients with few remaining options. Prospective studies are needed to establish specific treatment parameters.

The role of brachytherapy in the management of brain metastases: a systematic review

Purpose

Brain metastases have a highly variable prognosis depending on the primary tumor and associated prognostic factors. Standard of care for patients with these tumors includes craniotomy, stereotactic radiosurgery (SRS), or whole brain radiotherapy (WBRT) for patients with brain metastases. Brachytherapy shows great promise as a therapy for brain metastases, but its role has not been sufficiently explored in the current literature.

Material and methods

The PubMed, Cochrane, and Scopus databases were searched using a combination of search terms and synonyms for brachytherapy, brain neoplasms, and brain metastases, for articles published between January 1^st, 1990 and January 1^st, 2018. Of the 596 articles initially identified, 37 met the inclusion criteria, of which 14 were review articles, while the remaining 23 papers with detailing individual studies were fully analyzed.

Results

Most data focused on ¹²⁵I and suggested that it offers rates of local control and overall survival comparable to standard of care modalities such as SRS. However, radiation necrosis and regional recurrence were often high with this isotope. Studies using photon radiosurgery modality of brachytherapy have also been completed, resulting superior regional control as compared to SRS, but worse local control and higher rates of radiation necrosis than ¹²⁵I. More recently, studies using the ¹³¹Cs for brachytherapy offered similar local control and survival benefits to ¹²⁵I, with low rates of radiation necrosis.

Conclusions

For a variety of reasons including absence of physician expertise in brachytherapy, lack of published data on treatment outcomes, and rates of radiation necrosis, brachytherapy is not presently a part of standard paradigm for brain metastases. However, our review indicates brachytherapy as a modality that offers excellent local control and quality of life, and suggested that its use should be further studied.

Epilepsy in brain metastasis: an emerging entity

PURPOSE OF REVIEW

The purpose of this review is to highlight advances in the management of seizures in brain metastases from solid tumors.

RECENT FINDINGS

The highest risk for seizures is in patients with melanoma and lung cancer. There is lack of data on the efficacy of antiepileptic drugs (AEDs), but interactions between enzyme-inducing AEDs and anticancer agents must be avoided. Levetiracetam and valproic acid are the most appropriate drugs. Prophylaxis with AEDs for patients with brain metastases without a history of seizures is not recommended. Total resection of a brain metastasis allows complete seizure control. Seizures may represent an adverse effect of stereotactic radiosurgery or of high-dose chemotherapy. New preclinical and clinical studies should define the risk of brain metastasis in light of the new treatment options in the different tumor types. New clinical trials should be designed in patients with brain metastases in terms of treatment or prophylaxis of seizures.

Brachytherapy for meningiomas

Interstitial intracranial radiotherapy implants, or brachytherapy, is an adjuvant option for treatment of recurrent high-grade meningiomas after resection. The implants are placed in the resection cavity following tumor resection. The most commonly used isotope is Iodine-125 (I-125). While there are no controlled studies comparing treatment of meningiomas with or without brachytherapy, several case series report good long-term survival, suggesting that this may be a useful adjuvant for recurrent high-grade tumors. Complications can occur including radiation necrosis, impaired wound healing, hydrocephalus and infection. In the future, new isotopes are being explored that may have fewer complications and better safety profiles.

The American Brachytherapy Society consensus statement on intraoperative radiation therapy

PURPOSE

Although radiation therapy has traditionally been delivered with external beam or brachytherapy, intraoperative radiation therapy (IORT) represents an alternative that may shorten the course of therapy, reduce toxicities, and improve patient satisfaction while potentially lowering the cost of care. At this time, there are limited evidence-based guidelines to assist clinicians with patient selection for IORT. As such, the American Brachytherapy Society presents a consensus statement on the use of IORT.

METHODS

Physicians and physicists with expertise in intraoperative radiation created a site-directed guideline for appropriate patient selection and utilization of IORT.

RESULTS

Several IORT techniques exist including radionuclide-based high-dose-rate, low-dose-rate, electron, and low-energy electronic. In breast cancer, IORT as monotherapy should only be used on prospective studies. IORT can be considered in the treatment of sarcomas with close/positive margins or recurrent sarcomas. IORT can be considered in conjunction with external beam radiotherapy for retroperitoneal sarcomas. IORT can be considered for colorectal malignancies with concern for positive margins and in the setting of recurrent gynecologic cancers. For thoracic, head and neck, and central nervous system malignancies, utilization of IORT should be evaluated on a case-by-case basis.

CONCLUSIONS

The present guidelines provide clinicians with a summary of current data regarding IORT by treatment site and guidelines for the appropriate patient selection and safe utilization of the technique. High-dose-rate, low-dose-rate brachytherapy methods are appropriate when IORT is to be delivered as are electron and low-energy based on the clinical scenario.

Brachytherapy with surgical resection as salvage treatment for recurrent high-grade meningiomas: a matched cohort study

PURPOSE

To evaluate surgical resection with brachytherapy placement as a salvage treatment in patients with recurrent high-grade meningioma who exhausted prior external beam treatment options.

METHODS

Single-center retrospective review of our institutional experience of brachytherapy implantation from 2012 to 2018. The primary outcome of the study was progression free survival (PFS). Secondary outcomes included overall survival (OS) and complications. A matched cohort of patients not treated with brachytherapy over the same time period was evaluated as a control group. All patients had received prior radiation treatment and underwent planned gross total resection (GTR) surgery.

RESULTS

A total of 27 cases were evaluated. Compared with prior treatment, brachytherapy implantation demonstrated a statistically significant improvement in tumor control [HR 0.316 (0.101 - 0.991), p = 0.034]. PFS-6 and PFS-12 were 92.3% and 84.6%, respectively. Compared with the matched control cohort, brachytherapy treatment demonstrated improved PFS [HR 0.310 (0.103 - 0.933), p = 0.030]. Overall survival was not statistically significantly different between groups [HR 0.381 (0.073 - 1.982), p = 0.227]. Overall postoperative complications were comparable between groups, although there was a higher incidence of radiation necrosis in the brachytherapy cohort.

CONCLUSION

Brachytherapy with planned GTR improved PFS in recurrent high-grade meningioma patients who exhausted prior external beam radiation treatment options. Future improvement of brachytherapy dose delivery methods and techniques may continue to prolong control rates and improve outcomes for this challenging group of patients.

Placement of 131Cs permanent brachytherapy seeds in a large combined cavity of two resected brain metastases in one setting: case report and technical note

Large brain metastases are presently treated with surgical resection and adjuvant radiotherapy. However, local control (LC) for large tumors decreases from over 90% to as low as 40% as the tumor/cavity increases. Intraoperative brachytherapy is one of the focal radiotherapy techniques, which offers a convenient option of starting radiation therapy immediately after resection of the tumor and shows at least an equivalent LC to external techniques. Our center has pioneered this treatment with a novel FDA-cleared cesium-131 (¹³¹Cs) radioisotope for the resected brain metastases, and published promising results of our prospective trial showing superior results from ¹³¹Cs application to the large tumors (90%). We report a 57-year-old male patient, with metastatic hypopharyngeal brain cancer. The patient presented with two metastases in the right frontal and right parietal lobes. Post-resection of these lesions resulted in a large total combined cavity diameter of 5.3 cm, which was implanted with ¹³¹Cs seeds. The patient tolerated the procedure well, with 100% local control and 0% radiation necrosis. This case is unique in demonstrating that the ¹³¹Cs isotope was not only a convenient option of treating two resected brain metastases in one setting, but also that this treatment option offered excellent long-term LC and minimal toxicity rates.

Novel bioerodable eluting-spacers for radiotherapy applications with in situ dose painting

OBJECTIVE

To investigate feasibility of using bioerodable/bioerodible spacers (BES) over biodegradable spacers (BDS) loaded with gold nanoparticles for radiotherapy applications with in situ dose-painting, and to explore dosimetric impact on dose enhancement ratio of different radioisotopes.

METHODS

Analytical models proposed were based on experimentally reported erosion rate constant (k ₀ = 5. 5E-7 kgm^{- 2}s^{- 1} ) for bioerodible polymeric matrix. An in vivo determined diffusion coefficient (2.2E-8 cm²/s) of 10 nm gold nanoparticles (AuNP) of concentration 7 mg/g was used to estimate diffusion coefficient of other AuNP sizes (2, 5, 14 nm) using the Stoke-Einstein diffusion equation. The corresponding dose enhancement factors (DEF) were used to study dosimetric feasibility of employing AuNP-eluting BPS for radiotherapy applications.

RESULTS

The results showed AuNP release period from BES was significantly shorter (116 h) compared to BDS (more than a month) reported previously. The results also agree with reported Hopfenberg equation for a cylindrical matrix undergoing surface erosion. The DEF at tumour distance 5 mm for Cs-131 (DEF > 2.2) greater than that of I-125 (DEF > 2) and Pd-103 (DEF ≥ 2) could be achieved for AuNP sizes (2, 5, 10, and 14 nm) respectively.

CONCLUSION

Our findings suggested that BES could be used for short-lived radioisotopes like Pd-103 and Cs-131 in comparison to eluting BDS which is feasible for long-lived radioisotopes like I-125.

ADVANCES IN KNOWLEDGE

The study provides scientific basis for development of new generation eluting spacers viable for enhancing localized tumour dose. It concludes that BES gives higher DEF for Cs-131, and good candidate for replacing conventional fiducials/spacers.

Intraoperative brachytherapy for resected brain metastases

Brain metastases are the most common intracranial malignancies in adults. Surgical resection is the preferred treatment approach when a pathological diagnosis is required, for symptomatic patients who are refractory to steroids, and to decompress lesions causing mass effect. Radiotherapy is administered to improve local control rates after surgical resection. After a brief review of the literature describing the treatment of brain metastases using whole-brain radiotherapy, postoperative stereotactic radiosurgery, preoperative radiosurgery, and brachytherapy, we compare patient-related, technical, practical, and radiobiological considerations of each technique. Finally, we focus our discussion on intraoperative brachytherapy, with an emphasis on the technical aspects, benefits, efficacy, and outcomes of studies utilizing permanent Cs-131 implants.

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

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.

Resection Cavity Contraction Effects in the Use of Radioactive Sources (1-25 versus Cs-131) for Intra-Operative Brain Implants

Background and Objectives Intra-parenchymal brain surgical resection cavities usually contract in volume following low dose rate (LDR) brachytherapy implants. In this study, we systematically modeled and assessed dose variability resulting from such changes for I-125 versus Cs-131 radioactive sources. Methods Resection cavity contraction was modeled based on 95 consecutive patient cases, using surveillance magnetic resonance (MR) images. The model was derived for single point source geometry and then fully simulated in 3D where I-125 or Cs-131 seeds were placed on the surface of an ellipsoidal resection cavity. Dose distribution estimated via TG-43 calculations and biological effective dose (BED) calculations were compared for both I-125 and Cs-131, accounting for resection cavity contractions. Results Resection cavity volumes were found to contract with an effective half-life of approximately 3.4 months (time to reach 50% of maximum volume contraction). As a result, significant differences in dose distributions were noted between I-125 and Cs-131 radioactive sources. For example, when comparing with static volume, assuming no contraction effect, I-125 exhibited a 31.8% and 30.5% increase in D90 and D10 values (i.e., the minimal dose to 90% and 10% of the volume respectively) in the peripheral target areas over the follow-up period of 20.5 months. In contrast, Cs-131 seeds only exhibited a 1.44% and 0.64% increase in D90 and D10 values respectively. Such discrepancy is likewise similar for BED calculations. Conclusion Resection cavity contractions affects Cs-131 dose distribution significantly less than that of I-125 for permanent brain implants. Care must be taken to account for cavity contractions when prescribing accumulative doses of a radioactive source in performing the brain implant procedures.

Surgical Resection and Interstitial Iodine-125 Brachytherapy for High-Grade Meningiomas: A 25-Year Series

BACKGROUND

Atypical and malignant meningiomas can recur despite resection and radiation.

OBJECTIVE

To determine outcomes of patients with recurrent atypical or malignant meningioma treated with repeat resection and permanent iodine-125 ( 125 I) brachy-therapy.

METHODS

Charts of patients who underwent surgical resection and 125 I brachyther-apy implantation for atypical and malignant meningiomas between 1988 and 2013 were retrospectively reviewed. The Kaplan-Meier actuarial method was used to calculate progression-free and overall survival. The log-rank test was used to compare groups. Significance was set at P < .05.

RESULTS

Forty-two patients underwent 50 resections with 125 I brachytherapy im-plantations. All patients had undergone previous resections and 85% had previously undergone radiation. Median follow-up was 7.5 years after diagnosis and 2.3 years after brachytherapy. Median time to progression after resection with 125 I brachytherapy was 20.9 months for atypical meningioma, 11.4 months for malignant meningioma, and 11.4 months for the combined groups. Median survival after re-resection and 125 I brachytherapy was 3.5 years for atypical meningioma, 2.3 years for malignant menin-gioma, and 3.3 years for all subjects. Median overall survival after diagnosis was 11.1 years for atypical meningioma, 9.1 years for malignant meningioma, and 9.4 years for all subjects. Complications occurred in 17 patients and included radiation necrosis (n = 8, 16%), wound breakdown (n = 6, 12%), hydrocephalus (n = 4, 8%), infection (n = 3, 6%), and a pseudomeningocele (n = 2, 5%).

CONCLUSION

This is the largest experience with adjuvant 125 I brachytherapy for recurrent high-grade meningiomas. The outcomes support the use of adjuvant brachytherapy as an option for these aggressive tumors.

[Delineation of the surgical bed of operated brain metastases treated with adjuvant stereotactic irradiation: A review]

Stereotactic radiotherapy of the surgical bed of brain metastases is a technique that comes supplant indications of adjuvant whole brain radiotherapy after surgery. After a growing number of retrospective studies, a phase III trial has been presented and validated this indication. However, several criteria such as the dose, the fractionation, the use of a margin and definition of volumes remain to be defined. Our study consisted in making a literature review in order to provide a guideline of delineation of surgical beds of brain metastases, as well as the different modalities of their implementation process.

Resection and brain brachytherapy with permanent iodine-125 sources for brain metastasis

OBJECTIVE Stereotactic radiosurgery (SRS) with or without whole-brain radiotherapy can be used to achieve local control (> 90%) for small brain metastases after resection. However, many brain metastases are unsuitable for SRS because of their size or previous treatment, and whole-brain radiotherapy is associated with significant neurocognitive morbidity. The purpose of this study was to investigate the efficacy and toxicity of surgery and iodine-125 (¹²⁵I) brachytherapy for brain metastases. METHODS A total of 95 consecutive patients treated for 105 brain metastases at a single institution between September 1997 and July 2013 were identified for this analysis retrospectively. Each patient underwent MRI followed by craniotomy with resection of metastasis and placement of ¹²⁵I sources as permanent implants. The patients were followed with serial surveillance MRIs. The relationships among local control, overall survival, and necrosis were estimated by using the Kaplan-Meier method and compared with results of log-rank tests and multivariate regression models. RESULTS The median age at surgery was 59 years (range 29.9-81.6 years), 53% of the lesions had been treated previously, and the median preoperative metastasis volume was 13.5 cm³ (range 0.21-76.2 cm³). Gross-total resection was achieved in 81% of the cases. The median number of ¹²⁵I sources implanted per cavity was 28 (range 4-93), and the median activity was 0.73 mCi (range 0.34-1.3 mCi) per source. A total of 476 brain MRIs were analyzed (median MRIs per patient 3; range 0-22). Metastasis size was the strongest predictor of cavity volume and shrinkage (p < 0.0001). Multivariable regression modeling failed to predict the likelihood of local progression or necrosis according to metastasis volume, cavity volume, or the rate of cavity remodeling regardless of source activity or previous SRS. The median clinical follow-up time in living patients was 14.4 months (range 0.02-13.6 years), and crude local control was 90%. Median overall survival extended from 2.1 months in the shortest quartile to 62.3 months in the longest quartile (p < 0.0001). The overall risk of necrosis was 15% and increased significantly for lesions with a history of previous SRS (p < 0.05). CONCLUSIONS Therapeutic options for patients with large or recurrent brain metastases are limited. Data from this study suggest that resection with permanent ¹²⁵I brachytherapy is an effective strategy for achieving local control of brain metastasis. Although metastasis volume significantly influences resection cavity size and remodeling, volumetric parameters do not seem to influence local control or necrosis. With careful patient selection, this treatment regimen is associated with minimal toxicity and can result in long-term survival for some patients. ▪ CLASSIFICATION OF EVIDENCE Type of question: therapeutic; study design: retrospective case series; evidence: Class IV.

Cesium-131 brachytherapy for recurrent brain metastases: durable salvage treatment for previously irradiated metastatic disease

OBJECTIVE Managing patients whose intraparenchymal brain metastases recur after radiotherapy remains a challenge. Intraoperative cesium-131 (Cs-131) brachytherapy performed at the time of neurosurgical resection may represent an excellent salvage treatment option. The authors evaluated the outcomes of this novel treatment with permanent intraoperative Cs-131 brachytherapy. METHODS Thirteen patients with 15 metastases to the brain that recurred after stereotactic radiosurgery and/or whole brain radiotherapy were treated between 2010 and 2015. Stranded Cs-131 seeds were placed as a permanent volume implant. Prescription dose was 80 Gy at 5-mm depth from the resection cavity surface. The primary end point was resection cavity freedom from progression (FFP). Resection cavity freedom from progression (FFP), regional FFP, distant FFP, median survival, overall survival (OS), and toxicity were assessed. RESULTS The median duration of follow-up after salvage treatment was 5 months (range 0.5-18 months). The patients' median age was 64 years (range 51-74 years). The median resected tumor diameter was 2.9 cm (range 1.0-5.6 cm). The median number of seeds implanted was 19 (range 10-40), with a median activity per seed of 2.25 U (range 1.98-3.01 U) and median total activity of 39.6 U (range 20.0-95.2 U). The 1-year actuarial local FFP was 83.3%. The median OS was 7 months, and 1-year OS was 24.7%. Complications included infection (3), pseudomeningocele (1), seizure (1), and asymptomatic radionecrosis (RN) (1). CONCLUSIONS After failure of prior irradiation of brain metastases, re-irradiation with intraoperative Cs-131 brachytherapy implants provides durable local control and limits the risk of RN. The authors' initial experience demonstrates that this treatment approach is well tolerated and safe for patients with previously irradiated tumors after failure of more than 1 radiotherapy regimen and that it results in excellent response rates and minimal toxicity.

The Current and Future Treatment of Brain Metastases

Brain metastases are the most common intracranial malignancy, accounting for significant morbidity and mortality in oncology patients. The current treatment paradigm for brain metastasis depends on the patient’s overall health status, the primary tumor pathology, and the number and location of brain lesions. Herein, we review the modern management options for these tumors, including surgical resection, radiotherapy, and chemotherapy. Recent operative advances, such as fluorescence, confocal microscopy, and brachytherapy, are highlighted. With an increased understanding of the pathophysiology of brain metastasis come increased future therapeutic options. Therapy targeted to specific tumor molecular pathways, such as those involved in blood–brain barrier transgression, cell–cell adhesion, and angiogenesis, are also reviewed. A personalized plan for each patient, based on molecular characterizations of the tumor that are used to better target radiotherapy and chemotherapy, is undoubtedly the future of brain metastasis treatment.