How Does Brainstem Involvement Affect Prognosis in Patients with Limited Brain Metastases? Results of a Matched-Cohort Analysis

Stereotactic radiosurgery and radiotherapy for brainstem metastases: An international multicenter analysis

Brainstem metastases (BSM) present a significant neuro-oncological challenge, resulting in profound neurological deficits and poor survival outcomes. Stereotactic radiosurgery (SRS) and fractionated stereotactic radiotherapy (FSRT) offer promising therapeutic avenues for BSM despite their precarious location. This international multicenter study investigates the efficacy and safety of SRS and FSRT in 136 patients with 144 BSM treated at nine institutions from 2005 to 2022. The median radiographic and clinical follow-up periods were 6.8 and 9.4 months, respectively. Predominantly, patients with BSM were managed with SRS (69.4%). The median prescription dose and isodose line for SRS were 18 Gy and 65%, respectively, while for FSRT, the median prescription dose was 21 Gy with a median isodose line of 70%. The 12-, 24-, and 36-month local control (LC) rates were 82.9%, 71.4%, and 61.2%, respectively. Corresponding overall survival rates at these time points were 61.1%, 34.7%, and 19.3%. In the multivariable Cox regression analysis for LC, only the minimum biologically effective dose was significantly associated with LC, favoring higher doses for improved control (in Gy, hazard ratio [HR]: 0.86, p < .01). Regarding overall survival, good performance status (Karnofsky performance status, ≥90%; HR: 0.43, p < .01) and prior whole brain radiotherapy (HR: 2.52, p < .01) emerged as associated factors. In 14 BSM (9.7%), treatment-related adverse events were noted, with a total of five (3.4%) radiation necrosis. SRS and FSRT for BSM exhibit efficacy and safety, making them suitable treatment options for affected patients.

Clinical and radiographic adverse events after Gamma Knife radiosurgery for brainstem lesions: A dosimetric analysis

OBJECTIVES

To analyze the association between dosvolume relationships and adverse events in brainstem lesions treated with Gamma Knife radiosurgery (GKRS).

METHODS

Treatment plans were generated on BrainLab Elements and GammaPlan software. Dosimetric data were analyzed as continuous variables for patients who received GKRS to brain metastases or arteriovenous malformations (AVM) within or abutting the brainstem. Adverse events were classified as clinical and/or radiographic. Logistic and cox regression were used to assess the relationship between dosimetric variables and adverse events.

RESULTS

Sixty-one patients who underwent single fraction GKRS for brain metastases or AVM were retrospectively analyzed. Median age was 62 years (range: 12-92 years) and the median prescription dose was 18 Gy (range: 13-25 Gy). Median follow-up was 6months. Clinical and radiographic complications were seen in ten (16.4%) and 17 (27.9%) patients, respectively. On logistic regression, increasing D_05% was found to be associated with an increased probability of developing a clinical complication post-GKRS (OR: 1.18; 95% CI: 1.01-1.39; p = 0.04). Furthermore, mean brainstem dose (HR: 1.43; 95% CI: 1.05-1.94; p < 0.02), D_05% (HR: 1.09; 95% CI: 1.01-1.18; p = 0.03), and D_95% (HR: 2.37; 95% CI: 0.99-5.67; p = 0.05) were associated with an increased hazard of experiencing post-GKRS complications over time.

CONCLUSIONS

Increasing D_05% to the brainstem is associated with an increased risk of developing clinical complications. Clinicians may consider this parameter in addition to fractionated stereotactic radiation therapy when well-established dose constraints are not met in this patient population. Additional data are needed to further validate these findings.

The effect of brain metastasis location on clinical outcomes: A review of the literature

It is common clinical practice to consider the location of a brain metastasis when making decisions regarding local therapies and, in some scenarios, estimating clinical outcomes, such as local disease control and patient survival. However, the location of a brain metastasis is not included in any validated prognostic nomogram and it is unclear if this is due to a lack of a relationship or a lack of support from published data. We performed a comprehensive review of the literature focusing on studies that have investigated a relationship between brain metastasis location and clinical outcomes, including patient survival. The vast majority of reports anatomically categorized brain metastases as supratentorial or infratentorial whereas some reports also considered other subdivisions of the brain, including different lobes or with particular areas defined as eloquent cortex. Results were variable across studies, with some finding a relationship between metastasis location and survival, but the majority finding either no relationship or a weak correlation that was not significant in the context of multivariable analysis. Here, we highlight the key findings and limitations of many studies, including how neurosurgical resection might influence the relative importance of metastasis location and in what ways future analyses may improve anatomical categorization and resection status.

Postoperative Cavity Stereotactic Radiosurgery for Brain Metastases

During the past decade, tumor bed stereotactic radiosurgery (SRS) after surgical resection has been increasingly utilized in the management of brain metastases. SRS has risen as an alternative to adjuvant whole brain radiation therapy (WBRT), which has been shown in several studies to be associated with increased neurotoxicity. Multiple recent articles have shown favorable local control rates compared to those of WBRT. Specifically, improvements in local control can be achieved by adding a 2 mm margin around the resection cavity. Risk factors that have been established as increasing the risk of local recurrence after resection include: subtotal resection, larger treatment volume, lower margin dose, and a long delay between surgery and SRS (>3 weeks). Moreover, consensus among experts in the field have established the importance of (a) fusion of the pre-operative magnetic resonance imaging scan to aid in volume delineation (b) contouring the entire surgical tract and (c) expanding the target to include possible microscopic disease that may extend to meningeal or venous sinus territory. These strategies can minimize the risks of symptomatic radiation-induced injury and leptomeningeal dissemination after postoperative SRS. Emerging data has arisen suggesting that multifraction postoperative SRS, or alternatively, preoperative SRS could provide decreased rates of radiation necrosis and leptomeningeal disease. Future prospective randomized clinical trials comparing outcomes between these techniques are necessary in order to improve outcomes in these patients.

Toxicity of Radiosurgery for Brainstem Metastases

BACKGROUND

Although stereotactic radiosurgery (SRS) is an effective modality in the treatment of brainstem metastases (BSM), radiation-induced toxicity remains a critical concern. To better understand how severe or life-threatening toxicity is affected by the location of lesions treated in the brainstem, a review of all available studies reporting SRS treatment for BSM was performed.

METHODS

Twenty-nine retrospective studies investigating SRS for BSM were reviewed.

RESULTS

The rates of grade 3 or greater toxicity, based on the Common Terminology Criteria for Adverse Events, varied from 0 to 9.5% (mean 3.4 ± 2.9%). Overall, the median time to toxicity after SRS was 3 months, with 90% of toxicities occurring before 9 months. A total of 1243 cases had toxicity and location data available. Toxicity rates for lesions located in the medulla were 0.8% (1/131), compared with midbrain and pons, respectively, 2.8% (8/288) and 3.0% (24/811).

CONCLUSIONS

Current data suggest that brainstem substructure location does not predict for toxicity and lesion volume within this cohort with median tumor volumes 0.04-2.8 cc does not predict for toxicity.

Brain metastases: radiosurgery

Stereotactic radiosurgery has revolutionized the management of brain metastases. It delivers focused, highly conformal, ionizing radiation to a tumor delineated using high-resolution imaging, with low toxicity to adjacent brain structures. Randomized controlled and prospective trials have demonstrated a survival advantage and high local control rates after stereotactic radiosurgery for metastatic disease to the central nervous system, including for up to 10 brain metastases. Its minimal-access nature makes it an attractive alternative to surgical resection. Furthermore, in addition to chemotherapy, newer targeted therapies and immunotherapies with improved side-effect profiles allow for the concurrent delivery of systemic therapy with radiosurgery, with possible additive or synergistic effects, expediting the treatment of both extracranial and intracranial disease. The modern management of brain metastasis patients should include consideration of routine staging and surveillance magnetic resonance imaging scans in patients with higher-stage cancer to detect intracranial metastases earlier and treat promptly with radiosurgery in order to prevent the development of neurologic symptoms and the need for surgical resection.

Brainstem metastases treated with Gamma Knife stereotactic radiosurgery: the Indiana University Health experience

Brainstem metastases offer a unique challenge in cancer treatment, yet stereotactic radiosurgery (SRS) has proven to be an effective modality in treating these tumors. This report discusses the clinical outcomes of patients with brainstem metastases treated at Indiana University with Gamma Knife (GK) radiosurgery from 2008 to 2016. 19 brainstem metastases from 14 patients who had follow-up brain imaging were identified. Median tumor volume was 0.04 cc (range: 0.01–2.0 cc). Median prescribed dose was 17.5 Gy to the 50% isodose line (range: 14–22 Gy). Median survival after GK SRS treatment to brainstem lesion was 17.2 months (range: 2.8–45.6 months). The experience at Indiana University confirms the safety and efficacy of range of GK SRS prescription doses (14–22 Gy) to brainstem metastases.

Evaluation of outcomes after stereotactic radiosurgery for pilocytic astrocytoma

Pilocytic astrocytomas are rare intracranial gliomas that are typically treated with surgical extirpation. Our aim was to report the radiologic and clinical outcomes of patients treated with stereotactic radiosurgery (SRS) for pilocytic astrocytoma in the primary and salvage setting. Patients with pilocytic astrocytoma treated at a single institution with SRS from 1990 to 2015 were reviewed. Patient, disease, and treatment characteristics were collected and overall survival, local control, and toxicity were evaluated. Twenty-eight consecutive patients (12 females and 16 males) with a median age of 17.4 years at SRS were identified. Overall, 46% of patients were treated with SRS as part of the initial treatment course after biopsy or subtotal resection, and the remainder as a salvage therapy. The most common location was the cerebellum (28%) followed by brainstem and basal ganglia (21 and 18%, respectively). Four patients received prior external beam radiation therapy (14%). Median tumor volume was 1.84 cc (0.19-15.94 cc), and 39% had a cystic component at SRS. Prescription dose ranged from 4 to 20 Gy (median 16 Gy) to a median isodose line of 50% (range 30-100%). With a median follow-up of 5.2 years (0.3-17.1 years), all patients remained alive at last follow-up. Two patients demonstrated evidence of local radiographic progression at last follow-up (7%). No toxicity could be directly attributed to SRS. In this SRS series, durable tumor control was achieved in 93% of patients with pilocytic astrocytoma, although continued follow up will be important giving the natural history of this disease. As demonstrated, SRS is an appropriate technique in the primary and recurrent treatment of pilocytic astrocytoma that offers favorable disease control and infrequent clinical toxicity.

Radiosurgery for brainstem metastases with and without whole brain radiotherapy: clinical series and literature review

OBJECTIVE

The objective of this study was to investigate outcomes for patients with brainstem metastases treated with stereotactic radiosurgery (SRS).

METHODS

Patients with brainstem metastases treated with SRS between April 2006 and June 2012 were identified from a prospective database. Patient and treatment-related factors were recorded. Kaplan-Meier analysis was used to calculate survival and freedom from local and distant brain progression. Univariate and multivariate Cox regression was used to identify factors important for overall survival.

RESULTS

In total, 44 patients received SRS for 48 brainstem metastases of whom 33 (75 %) also received whole brain radiotherapy (WBRT): 23 patients (52 %) WBRT prior to SRS, 6 (13.6 %) WBRT concurrently with SRS and 4 (9.0 %) WBRT after SRS. Eight patients received a second course of WBRT at further progression. Median target volume was 1.33 cc (range 0.04-12.17) and median prescribed marginal dose was 15 Gy (range 10-22). There were four cases of local failure, and 6-month and 1-year freedom from local failure was 84.6 and 76.9 %, respectively. Median overall survival (OS) was 5.4 months. There were four cases of radionecrosis, 2 (4.8 %) of which were symptomatic. The absence of external beam brain radiotherapy (predominantly WBRT) showed a trend towards improved OS on univariate analysis. Neither local nor distant brain failure significantly impacted OS.

CONCLUSION

This retrospective series of patients treated with SRS for brainstem metastases, largely in combination with at least one course of WBRT, demonstrates that this approach is safe and results in good local control. In this cohort, no variables significantly impacted OS, including intracranial control.

Stereotactic Radiosurgery for Brainstem Metastases: An International Cooperative Study to Define Response and Toxicity

PURPOSE

To pool data across multiple institutions internationally and report on the cumulative experience of brainstem stereotactic radiosurgery (SRS).

METHODS AND MATERIALS

Data on patients with brainstem metastases treated with SRS were collected through the International Gamma Knife Research Foundation. Clinical, radiographic, and dosimetric characteristics were compared for factors prognostic for local control (LC) and overall survival (OS) using univariate and multivariate analyses.

RESULTS

Of 547 patients with 596 brainstem metastases treated with SRS, treatment of 7.4% of tumors resulted in severe SRS-induced toxicity (grade ≥3, increased odds with increasing tumor volume, margin dose, and whole-brain irradiation). Local control at 12 months after SRS was 81.8% and was improved with increasing margin dose and maximum dose. Overall survival at 12 months after SRS was 32.7% and impacted by age, gender, number of metastases, tumor histology, and performance score.

CONCLUSIONS

Our study provides additional evidence that SRS has become an option for patients with brainstem metastases, with an excellent benefit-to-risk ratio in the hands of experienced clinicians. Prior whole-brain irradiation increases the risk of severe toxicity in brainstem metastasis patients undergoing SRS.