Cognitive cost or disease control in the management of brain metastases from small cell Lung cancer?—an ongoing debate

The study “Stereotactic radiosurgery in patients with small cell lung cancer and 1-10 brain metastases: a multi-institutional, phase II, prospective clinical trial” is a multi-institutional, phase II, prospective clinical trial that provides important prospective data on the use of stereotactic radiosurgery (SRS) or stereotactic radiotherapy (SRT) as first line treatment for patients with small cell lung cancer (SCLC) and 1–10 brain metastases, a population historically managed with whole brain radiotherapy (WBRT) (1). The trial enrolled 100 patients, with a median of two brain metastases, and excluded those with prior brain-directed radiation. According to the authors, the primary endpoint was neurologic death at 1 year, “defined as marked, progressive radiographic progression in the brain accompanied by corresponding neurologic symptomatology in the absence of systemic disease progression or systemic symptoms of a life-threatening nature”. In this case, 1-year neurologic death, which was 11.0% [95% confidence interval (CI): 5.8–18.1%], was notably lower than the historical WBRT rate of 17.5%. Median overall survival (OS) was 10.2 months, and only 22% required salvage WBRT, suggesting that SRS/SRT with close magnetic resonance imaging (MRI) surveillance could achieve acceptable neurologic outcomes and limit WBRT exposure (1).

The article is distinguished by its lucid exposition, its direct applicability to contemporary clinical practice, and its contribution to advancing the understanding of SRS as a feasible therapeutic modality for patients with SCLC presenting with limited brain metastases. The article’s findings are timely, given the increasing adoption of MRI surveillance and the shift away from prophylactic cranial irradiation in SCLC.

SRS and SRT are highly precise, image-guided radiation techniques that deliver ablative doses to discrete intracranial targets, typically in one (SRS) or a few (SRT) fractions. These modalities minimize radiation exposure to surrounding normal brain tissue, reducing neurocognitive toxicity compared to WBRT. This approach results in a marked reduction in acute and late neurotoxicity, including cognitive impairment, fatigue, and alopecia, which are more common with WBRT due to its diffuse exposure of healthy brain tissue. Table 1 shows a comparison of cognitive outcomes: WBRT vs. SRS.

SRS/SRT is increasingly considered for patients with a limited number of brain metastases because it also improves local control with minimal invasiveness and rapid recovery, making them especially valuable for patients with limited brain metastases and good performance status (7).

However, patients with SCLC and brain metastases have poor survival, with median OS typically ranging from 7 to 10 months, even with aggressive therapy (8), still limited by aggressive extracranial disease. Although SRS/SRT may be associated with a higher rate of distant brain failure, according to the FIRE-SCLC study data, this fact does not always translate into increased neurologic mortality when patients are closely monitored and receive timely salvage therapy as needed (9). This study showed that SRS/SRT provides similar or better OS compared to WBRT (median OS: 8.5–11 months for SRS vs. 5.2 months for WBRT). These findings are consistent with recent meta-analyses and cohort studies showing comparable or improved survival and local control with SRS compared to WBRT in selected SCLC patients (9-11). Emerging data also suggest that combining brain radiotherapy with immune checkpoint inhibitors and chemotherapy may further improve survival in extensive-stage SCLC with brain metastases (12).

In light of this, clinical guidelines for the management of patients with SCLC and brain metastases note that although new clinical data are emerging, evidence for SRS in SCLC is less robust than in non-SCLC (randomized trial data are lacking); therefore, they continue to recommend WBRT as the standard treatment, particularly for patients with multiple or symptomatic brain metastases. The American Society of Clinical Oncology (ASCO), the American Society for Radiation Oncology (ASTRO), and the Society for Neuro-Oncology (SNO) endorse WBRT for SCLC brain metastases, given the high risk of rapid intracranial progression and the limited evidence supporting focal therapies in this population (13,14).

International practice patterns and expert consensus further illustrate the variability and ongoing debate regarding the use of WBRT vs. SRS in SCLC with brain metastases. European expert panels, for example, demonstrate less uniformity than United States-based guidelines: among European oncologists and radiation oncologists, there is a tendency to recommend chemotherapy alone for asymptomatic patients, reserving WBRT primarily for symptomatic cases. In select patients with limited brain metastases, some European experts consider SRS as an alternative to WBRT, though this is not a universal practice and reflects significant variation in clinical decision-making across the continent (15).

Strengths of the study include its prospective, multi-institutional design and rigorous definition of neurologic death. The prospective design and multi-center enrollment enhance the validity and generalizability of the findings, and the use of a standardized, rigorous definition of neurologic death is a methodological advance over prior retrospective series. The study also reflects contemporary practice, with close MRI surveillance and exclusion of patients with prior brain-directed radiation, aligning with evolving management paradigms for SCLC brain metastases (10,11).

Additional strengths include the inclusion of patients with up to 10 metastases, which broadens applicability beyond the traditional 1–4 lesion threshold, and the demonstration of a relatively low rate of neurologic death (11% at 1 year) and limited need for salvage WBRT (22%), supporting the feasibility of SRS/SRT in this population. The median OS of 10.2 months is consistent with pooled data from meta-analyses and large cohort studies (16).

It is noteworthy to highlight that the table summarizing toxicities in the manuscript is detailed and provides information not only on neurologic death but also on other recorded symptoms, with a level of detail that is especially appreciated.

With a focus on elderly patients, since this trial included patients with a median age of 67 years (interquartile range, 61–73 years), and 32% of the cohort was aged 70 or older, findings have important implications for elderly or frail patient populations. SRS/SRT has demonstrated in this trial a low rate of neurologic death (11% at 1 year) and a reduced need for salvage WBRT, supporting its use as a first-line approach in selected patients with limited brain metastases and close MRI surveillance. For elderly and frail patients, this is particularly relevant because WBRT is associated with higher rates of neurocognitive decline, fatigue, and overall toxicity, which can significantly impact quality of life and functional status (17-21). Literature has also previously demonstrated that SRS/SRT offer a more favorable toxicity profile, showing that elderly patients (including those ≥75 years) tolerate this focal treatment well, maintain stable performance status, and do not experience increased rates of severe adverse events compared to younger cohorts (22).

However, several additional limitations merit consideration. The single-arm design precludes direct comparison with WBRT, and reliance on historical controls introduces potential confounding due to differences in patient selection, imaging frequency, and supportive care. Among the 100 patients enrolled, while the allowed number of brain metastases for patient enrollment was 1–10, the median number of metastases was low (3), with an interquartile range of 1–4 and a full range of 1–10. Hence, results may not fully extrapolate to real-life patients with higher intracranial disease burden. The majority of patients in the trial had a low intracranial disease burden, so the data are most robust for patients with 1–4 lesions. Outcomes for patients with higher numbers of metastases (6-11) are less certain, as only a minority of trial participants fell into this category. Without stratification or subgroup analysis by WBRT or SRS dose, the study cannot address whether certain dosing regimens are superior or safer, nor can it inform optimal dosing strategies for a specific patient. Additionally, the trial mandated close imaging-based surveillance and prompt salvage therapy, which may not be feasible in all clinical settings. Therefore, caution is warranted when applying these results to patients with more than two brain metastases, as efficacy and safety may differ in those with a higher intracranial disease burden or less intensive follow-up. Authors do not report the interval between relapses or recurrences of brain metastases. In the literature, studies of repeated SRS/SRT for recurrent brain metastases show that a longer interval between SRT sessions is associated with better neurological death-free survival (NDFS) and OS, with brain metastasis velocity (the rate of new metastases over time) serving as a key prognostic factor (23). The study does not specify the decision-making process for salvage therapy selection, which is a notable omission given the clinical relevance of this choice. Literature indicates that factors such as the number of new or progressive brain metastases, performance status, prior intracranial treatments, and extent of extracranial disease often guide the selection between salvage SRS and WBRT. SRS as salvage therapy is particularly beneficial for patients with a limited number of new lesions, who experience a longer interval free of relapse, as these patients tend to have lower brain metastasis velocity and better performance status, both of which are associated with improved outcomes after salvage SRS/SRT (24). The manuscript does not address the contribution of chemotherapy to neurological death in these patients. Neurologic death is defined and reported, but there is no analysis of whether the receipt, timing, or type of chemotherapy affected the risk of neurologic death. This is a notable omission, as the medical literature indicates that systemic therapy, including chemotherapy, has limited efficacy in controlling brain metastases from SCLC and does not significantly alter neurologic death rates, as summarized in the Cochrane review (25). However, the study in question does not provide data or commentary on this aspect. The study also failed to provide detailed quality of life outcomes, which are particularly important considering the rationale for preferring SRS/SRT over WBRT. There is also limited granularity regarding systemic therapy regimens, extracranial disease status, and volumetric intracranial tumor burden, all of which are important prognostic factors. Also, the relatively short follow-up may underestimate late CNS progression or neurotoxicity. The trial excluded patients with prior brain-directed radiation, significant comorbidities, and those unable to undergo close imaging surveillance, limiting generalizability to the broader SCLC population. Resource allocation and access could be another limitation, since SRS requires specialized technology and multidisciplinary expertise, which may not be available in all settings, raising public health concerns about equitable access (26). There is a selected group of patients with SCLC and brain metastases in real-world practice who, due to poor performance status, are not represented in this study. The ASTRO specifically recommends early palliative care and, in some cases, supportive care alone for patients with palliative needs and poor performance status and short-course WBRT regimens (e.g., 5 fractions) if radiotherapy is pursued (27). Nevertheless, it remains to be seen whether these recommendations of SRS/SRT might in the future also be extrapolated to this particular patient population. This aligns with palliative care goals of minimizing symptom burden and maximizing function (4). This is also consistent with the American College of Chest Physicians’ recommendations to prioritize symptom control and minimize toxicity in patients with brain metastases, especially those with limited life expectancy or poor performance status (28).

From a public health perspective, SRS/SRT for patients with SCLC and 1–10 brain metastases can reduce healthcare utilization by decreasing the need for prolonged WBRT and hospitalizations for neurotoxicity, but the implementation of these advanced techniques is limited by disparities in access to radiotherapy infrastructure, technology, and trained personnel. The medical literature highlights that radiotherapy access is highly variable globally, with significant deficits in equipment and workforce, especially in low- and middle-income countries, where only a minority of patients have timely access to modern radiotherapy modalities such as SRS/SRT (29,30). Investment in radiotherapy resources—including linear accelerators, radiosurgery platforms, and multidisciplinary training—is essential to ensure equitable access to effective and less toxic treatments. The Lancet Oncology Commission and the International Atomic Energy Agency emphasize that targeted investments, strategic facility placement, and workforce development are required to close the gap in radiotherapy access and to realize the health and economic benefits of modern cancer care (31,32). Diligent and active implementation of these technologies will improve outcomes and quality of life for patients with SCLC and brain metastases, while also reducing the overall burden on healthcare systems.

Emerging strategies such as hippocampal avoidance WBRT and neuroprotective agents (e.g., memantine) may mitigate cognitive toxicity, but direct comparisons with SRS/SRT are lacking. Ongoing randomized trials and real-world studies are essential to refine patient selection and optimize the balance between disease control and cognitive preservation in the management of brain metastases from SCLC.

Multidisciplinary decision-making is increasingly recognized as critical in neuro-oncology. Tumor boards and shared decision-making interventions have been shown to improve diagnostic accuracy, guide management, and enhance patient satisfaction. Personalized care should integrate patient values, the potential for neurocognitive preservation, performance status, molecular profiling, emerging therapies, incorporating patient preferences, as well as the risks of intracranial progression and systemic disease are essential to advance care for patients with SCLC and brain metastases (33).

Any improvement in outcomes, such as prolonging survival, reducing neurologic death, or preserving quality of life, would be clinically meaningful in this population. The debate between cognitive cost and disease control is unresolved. While SRS/SRT offers clear neurocognitive benefits, WBRT remains superior for intracranial control, particularly in patients with multiple or rapidly progressive metastases. The article includes clear writing, direct relevance to current clinical practice, and its illumination of SRS as a viable treatment option for SCLC patients with limited brain metastases.

In summary, this trial (1) provides important prospective evidence supporting SRS/SRT for selected SCLC patients with limited brain metastases, especially in the context of improved imaging and systemic therapies, but confirmatory randomized trials with comprehensive neurocognitive and quality-of-life endpoints are needed to fully establish SRS/SRT as standard of care in this setting.

Acknowledgments

None.

Footnote

Provenance and Peer Review: This article was commissioned by the editorial office, Annals of Palliative Medicine. The article did not undergo external peer review.

Funding: None.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://apm.amegroups.com/article/view/10.21037/apm-25-101/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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