In recent oncology practice, stereotactic radiotherapy brain metastases management has experienced dramatic therapeutic advancements. Historically, radiation oncologists reserved focused radiosurgery strictly for individuals harboring very few, small intracranial lesions. Patients presenting with numerous deposits or larger tumors usually received palliative whole-brain radiation therapy instead. However, widespread whole-brain irradiation frequently causes persistent neurocognitive deterioration and functional decline. Consequently, clinicians increasingly investigate whether targeted stereotactic radiotherapy can safely treat extensive intracranial disease without sacrificing patient safety. Therefore, establishing rigorous clinical evidence remains essential to expand treatment eligibility safely.

The Evolution of Stereotactic Radiotherapy Brain Metastases Care

For decades, neurosurgeons relied on rigid invasive frames to deliver stereotactic radiosurgery with submillimeter mechanical accuracy. While invasive head frames ensure exceptional target immobility, they restrict radiation delivery to a single exhaustive session. In contrast, modern frameless mask-based systems enable fractionated stereotactic radiotherapy without compromising stereotactic precision. Fractionated regimens exploit classic radiobiological principles, thereby protecting adjacent eloquent brain tissue and critical neural pathways. Furthermore, dividing high radiation doses into several fractions significantly lowers the cumulative danger of symptomatic radiation necrosis.

Consequently, frameless mask platforms empower radiation teams to treat larger tumors and complex intracranial targets. In addition, patients experience far greater physical comfort during immobilized procedures. Clinicians can also deliver multiple planned courses smoothly over several consecutive days. As a result, treatment teams can manage challenging anatomical geometries near the brainstem or optic apparatus with great confidence. Furthermore, the non-invasive mask system dramatically enhances overall patient compliance during extended fractionation schedules. Therefore, modern mask-based immobilization technology fundamentally transforms neuro-oncology treatment paradigms, allowing radiation oncologists to address extensive intracranial metastases safely.

Re-Examining the Historic JLGK0901 Clinical Criteria

The landmark Japanese JLGK0901 study established stereotactic radiosurgery as standard care for patients with multiple brain metastases. Specifically, the original trial confirmed equivalent survival between patients with five to ten lesions and those with two to four lesions. However, the trial strictly limited eligibility to patients whose cumulative tumor volume remained at or below fifteen milliliters. Additionally, investigators restricted individual lesion volumes to ten milliliters and maximum diameters to three centimeters.

Although these criteria provided essential safety boundaries, modern oncologists frequently treat patients exceeding these numeric thresholds. Consequently, clinicians questioned whether exceeding these historic restrictions compromises intracranial disease control. Furthermore, contemporary targeted therapies and immune checkpoint inhibitors significantly prolong systemic cancer survival. As systemic disease control improves, neuro-oncologists require robust data regarding stereotactic radiotherapy outcomes in extended disease profiles. Therefore, re-evaluating the rigid JLGK0901 boundaries represents a crucial objective in modern radiation oncology.

Study Design and Propensity Score Matching Methodology

To address this crucial clinical question, researchers at Rakusai Shimizu Hospital conducted a comprehensive retrospective investigation spanning six and a half years. The investigators analyzed 1,043 consecutive patients who received stereotactic radiotherapy for newly diagnosed brain metastases using a frameless mask system. Subsequently, the research team stratified the cohort into two distinct clinical groups based on the classic JLGK0901 criteria. Group A comprised 673 patients who met all standard criteria, representing 64.5 percent of the initial population. Conversely, Group B encompassed 370 patients with extended indications, exceeding the established volume or tumor number restrictions.

Because baseline clinical characteristics differed between the two groups, the investigators utilized rigorous propensity score matching to prevent confounding bias. Specifically, matching algorithms accounted for age, primary cancer histology, baseline performance scores, and active extracranial metastases. Consequently, this matching process created two well-balanced cohorts containing 321 patients each. By aligning these baseline prognostic variables, the study effectively isolated the independent therapeutic impact of stereotactic radiotherapy.

Comparative Outcomes: Neurological Mortality and Local Control

The primary endpoint of this comparative study focused specifically on the incidence of neurological death between both matched cohorts. Interestingly, the analysis revealed no statistically significant difference in neurological mortality between Group A and Group B. Neurological death rates remained comparable despite the higher tumor numbers and larger volumes present in the extended group. Moreover, local tumor control rates exhibited no significant statistical variation between the two matched populations. Similarly, the cumulative incidence of new intracranial lesions remained virtually identical throughout the follow-up period.

Nevertheless, overall median survival time was shorter in Group B compared to Group A, recording 10.6 months versus 19.7 months. This divergence in overall survival reflected advanced extracranial disease progression rather than neuro-oncological treatment failure. In addition, patients in both cohorts maintained equivalent neurological functional independence following their radiation regimens. Therefore, the findings demonstrate that stereotactic radiotherapy effectively suppresses intracranial disease progression even when tumors exceed traditional size and volume limits.

Adverse Events, Radiation Toxicity, and Quality of Life

Maintaining patient safety and preserving neurological function represent vital priorities when treating multiple brain metastases with targeted radiation. Fortunately, the study recorded remarkably low toxicity rates across both cohorts during long-term radiographic and clinical follow-up. Specifically, the incidence of symptomatic radiation necrosis remained minimal in both standard and extended cohorts. The routine application of fractionated stereotactic radiotherapy for larger lesions largely explains this favorable safety profile. By dividing radiation doses across successive sessions, clinicians successfully minimized healthy parenchymal injury.

Furthermore, the authors observed no significant differences in neurological deterioration between matched patient groups. Most patients preserved their baseline performance status, avoiding debilitating treatment-induced cognitive declines. Consequently, frameless mask-based radiation therapy demonstrated exceptional clinical tolerability even among individuals presenting with bulky or multifocal intracranial tumors. In addition, serial post-treatment neuroimaging demonstrated durable radiological disease stabilization across the vast majority of treated lesions. Therefore, clinicians can confidently administer targeted stereotactic treatments without fearing excessive treatment-related morbidity or functional decline.

Clinical Implications for Contemporary Neuro-Oncology Practice

These compelling findings offer immense practical relevance for multidisciplinary neuro-oncology teams managing brain metastases. Historically, clinicians routinely referred patients presenting with more than ten intracranial metastases or bulky tumors for whole-brain radiation therapy. However, whole-brain radiation frequently inflicts irreversible neurocognitive damage and impairs long-term quality of life. This contemporary matched analysis demonstrates that mask-based stereotactic radiotherapy provides robust intracranial control without elevating neurological mortality. Consequently, radiation oncologists can safely expand treatment eligibility to patients formerly deemed ineligible for stereotactic intervention.

Moreover, modern systemic therapies with high intracranial penetrance complement stereotactic radiotherapy exceptionally well. Because stereotactic approaches avoid whole-brain radiation toxicity, patients tolerate ongoing systemic chemotherapies, targeted therapies, and immunotherapies without interruption. In addition, mask-based fixation systems eliminate the invasive discomfort of surgical stereotactic pins. As a result, treatment centers can offer comfortable, repeatable outpatient radiotherapy regimens. Ultimately, these clinical insights support updating radiosurgical practice guidelines to broaden therapeutic options for complex cancer patients.

Frequently Asked Questions

What did the JLGK0901 study originally recommend for brain metastases?

The landmark JLGK0901 study confirmed that stereotactic radiosurgery alone is effective for patients with up to ten brain metastases. However, the trial strictly limited patient selection to cumulative intracranial volumes under fifteen milliliters and individual lesion volumes below ten milliliters, cautioning against treating larger or more numerous tumors.

How does mask-based stereotactic radiotherapy improve patient safety?

Mask-based stereotactic systems allow clinicians to deliver fractionated radiation regimens without invasive skull-anchored head frames. Dividing high radiation doses across multiple sessions reduces the risk of radiation necrosis and spares surrounding normal brain tissue, allowing safe and comfortable treatment for larger or complex intracranial lesions.

Why did overall survival differ if neurological mortality remained identical?

Although stereotactic radiotherapy achieved equivalent local tumor control and prevented neurological death in both cohorts, overall survival diverged because patients with extended intracranial disease often harbored aggressive, disseminated systemic cancer. Therefore, systemic extracranial progression dictated overall survival rather than intracranial therapeutic failure.

Disclaimer: This content is for informational and educational purposes only... Refer to the latest local and national guidelines for clinical practice.

References

Oi Y et al. A propensity score-matched analysis of stereotactic radiotherapy for metastatic brain tumors using the Leksell Gamma Knife Icon Mask system: a single-center retrospective comparative study of cases meeting and not meeting the JLGK0901 Criteria. J Neurosurg. 2025 Sep 01. doi: 10.3171/2025.1.JNS242424. PMID: 40344776.

Yamamoto M, Serizawa T, Shuto T, et al. Stereotactic radiosurgery for patients with multiple brain metastases (JLGK0901): a multi-institutional prospective observational study. Lancet Oncol. 2014;15(4):387-395.

Niranjan A, Monaco E, Flickinger J, Lunsford LD. Guidelines for Multiple Brain Metastases Radiosurgery. Prog Neurol Surg. 2019;34:100-109.